Soul-Body Dualism and Science

Stewart Goetz

This entry begins with a consideration of what a soul is and whether it is reasonable to believe in its existence. It then looks at what, if anything, the Bible teaches about the existence of the soul, and whether there are non-biblical reasons for believing in the soul’s existence. Some biblical scholars and theologians, in light of their awareness of developments in modern science, argue that a person who believes in science cannot consistently believe in the existence of the soul. They typically invoke discoveries by neurologists of mental-physical correlations and the use by all scientists of the principle of methodological causal closure to support their position. This entry examines these two issues and concludes with brief treatments of the soul’s existence and relationship to the purpose of life, life after death, and abortion.

1 What is a soul?

1.1 A philosophical overview of the mental nature of a soul

When C. S. Lewis, an Oxford academician and Christian, was asked ‘What is a soul?’, he answered, ‘I am. (This is the only possible answer: or expanded, “A soul is that which can say I am”)’ (Lewis 2007: 10). What is noteworthy for the purposes of this entry is that, even though Lewis was a Christian, he did not frame his answer in Jewish-Christian theological or scriptural terms. And while this entry will treat a few theological and scriptural topics related to the soul in a modicum of depth, it too is not framed in such terms. This is because the concept of the soul is philosophically generic in nature and as such transcends any specific religious tradition.

Lewis wrote that he was a soul. Down through the ages, there have been disputes about whether, strictly speaking, the first-person pronoun ‘I’ refers, as Lewis’ answer suggests, to the soul alone (or the mind alone, where ‘soul’ and ‘mind’ are used interchangeably) as opposed to the soul and its physical (material) body (the soul-body complex) together. However, on either understanding of what it is to which ‘I’ refers, the soul is regarded as the subject of the mental capacities which are the central concern of those who seek to understand the relationship between science and the soul (see The History of Science and Theology). Therefore, for the purpose of simplicity, this entry will assume that the soul alone with its mental capacities is the referent of ‘I’.

A soul’s mental capacities are a species of its generic psychological capacities (another species of the psychological is the qualitative; see section 1.1.2). What makes a psychological capacity mental in nature? A capacity is mental in nature whose actualization (an event) is a propositional attitude about an object or objects in the world (i.e. trees, mountains, automobiles, quarks, computers, other people, God, etc.). Thoughts (actualizations of the capacity to think), beliefs (actualizations of the capacity to believe), desires (actualizations of the capacity to desire), and choices (actualizations of the capacity to choose) are instances of propositional attitudes. An attitude is propositional in nature in terms of its content which provides the attitude with its directedness at an object in the world. For example, we (souls) can desire and choose to order a meal, where the desiring and choosing are propositional attitudes directed at the content ‘that we order a meal’ (‘to order a meal’). Of particular interest in this entry is the fact that our choices are explained by purposes (reasons). For example, if we choose to order a meal we might do so for the purpose ‘that we satisfy our desire to eat’. In philosophical terminology, purposes are teleological explanations, where a teleological explanation is an explanation that is stated in terms of a goal, aim, or end.

We choose to order a meal for the purpose that we satisfy our desire to eat. Ordering a meal can be done in different ways. Occasionally, we order a meal by telling someone else (e.g. a waiter or waitress) what we desire to eat. Telling someone else what we want to eat involves movements of our mouths in sophisticated ways which express contents. How do we move our mouths on those occasions when we order a meal? For the sake of discussion, it is assumed that something like the following occurs (see Kim 1996: 131–132): physical nerve impulses reach the relevant muscles in the areas of our mouths which lead to the muscles contracting in certain ways. Presumably, the nerve signals are caused by the activation of certain neurons in our brains, which are ultimately caused to fire by the choice to order the meal for the stated purpose. In other words, at some spatial location, presumably in our brains, there is direct (unmediated) mental-to-physical causal interaction between our choices and the relevant physical neural events (or some other physical events which cause the relevant neural events) in our brains.

1.1.1 Substance versus property dualism

The points made in section 1.1 concern the soul and its relationship with its physical body. According to the philosophical view known as soul-body substance dualism, or substance dualism for short, an individual human being is comprised of two substances: a soul and its physical body (‘body’ for short). There is another kind of dualism, what is called property dualism or dual-aspect dualism, which is the view that there is one substance, a body (or brain), that has two kinds of capacities, physical and psychological, where some of the latter are mental in nature. One of the implications of substance, but not property, dualism is the possibility for the soul to exist without its body (exist in a disembodied state) or to be re-embodied in a different body. This entry is primarily concerned with substance dualism, though property dualism will be discussed briefly in section 3 below. As will become evident in section 3, substance dualism is itself a genus of which there are species (creationist and emergentist).

1.1.2 Why be a substance dualist?

The philosopher of cognitive science, Aku Visala, writes that

[t]raditionally, theologians and philosophers in the West have thought that human persons are either identical to or constituted partly by souls […] One of the historically most powerful arguments for the existence of the soul was that a non-natural, non-material entity was the best explanation for our higher-level mental capacities. (Visala 2015: 65)

A couple of pages later, Visala asserts that ‘Christian theological anthropology has tended to affirm a set of common-sense assumptions about the nature of human persons’, which include ‘the claim that we are self-conscious agents who are morally responsible and who retain an identity over the course of [our] earthly lives and even in bodily death and resurrection’ (Visala 2015: 67). While there is no good reason to contest what Visala asserts in these passages, it is important to point out one thing that he fails explicitly to state, which is that the view of ordinary/everyday people (individuals who are not educated philosophically) – what is often referred to as common sense –ß includes the belief that we are souls which are distinct from and have physical bodies. That is, common sense includes the belief in substance dualism. The experimental cognitive scientist Jesse Bering writes that human beings commonsensically (naturally) believe in substance dualism (Bering 2006), and the psychologist Nicholas Humphrey (2011) insists that there is a human inclination to believe in substance dualism. Toward the end of his book Soul Dust, Humphrey mentions other scholars who acknowledge the existence of a natural belief in substance dualism (even though they, like Humphrey, have come to deny the existence of the soul and, thereby, substance dualism):

Thus, development psychologist Paul Bloom aptly describes human beings as ‘natural-born dualists.’ Anthropologist Alfred Gell writes: ‘It seems that ordinary human beings are “natural dualists,” inclined more or less from day one, to believe in some kind of “ghost in the machine” . . .’ Neuropsychologist Paul Broks writes: ‘The separateness of body and mind is a primordial intuition. . . Human beings are natural born soul makers, adept at extracting unobservable minds from the behaviour of observable bodies, including their own.’ (Humphrey 2011: 195)

Even Charles Darwin recognized that ordinary people believe in the truth of substance dualism:

If […] we include under the term ‘religion’ the belief in unseen or spiritual agencies […] this belief seems to be universal with the less civilized races […] As Mr M’Lennan has remarked, ‘Some explanation of the phenomena of life, a man must feign for himself; and to judge from the universality of it, the simplest hypothesis and the first to occur to me, seems to have been that natural phenomena are ascribable to the presence in animals, plants, and things, and in the forces of nature, of such spirits prompting to action as men are conscious they themselves possess.’ (Darwin 1989: Part One, 98)

Why is it natural to believe in the existence of the soul? The short answer is that we are seemingly directly aware of ourselves as psychological substances that are simple in nature in the sense that we are not composed of other substances (see section 3.2), even though we possess a multiplicity of psychological capacities (e.g. the mental capacities already discussed in section 1.1, as well as the qualitative capacities to experience pleasure and pain).

It is important to stress that a belief in the soul’s existence, because of its naturalness or commonsensicality, is not theoretical in nature. That is, a belief in the soul is not an affirmation of the existence of an entity that is theorized and postulated to exist in order to explain something for which we have not been able to find any other plausible explanation. The neuropsychologist Malcolm Jeeves writes that

[s]ome [who affirm the existence of the soul] take a ‘soul-of-the-gaps’ position, much like the older ‘god-of-the-gaps’ position, using the concept of the ‘soul’ to explain those human experiences that we cannot (yet, at least) explain neurologically or biologically. (Jeeves 2004: 245)

Contrary to Jeeves, belief in the existence of the soul as the subject of psychological events (experiences) is commonsensical in nature. It is not arrived at on the basis of a theoretical need to postulate its existence as the locus of experiences for which no neurological or biological subject has been found.

Because many individuals who are interested in the relationship between science and the soul are also interested in the compatibility of beliefs in science and Christianity, it is prudent to take a moment to examine what, if anything, the Bible has to say about substance dualism.

1.2 The Bible and substance dualism

What do the Hebrew Bible (Christian Old Testament) and Christian New Testament have to say about the truth of substance dualism? Much ink has been spilt in addressing this question, but plausibly the answer one gives to it in part reflects what one believes about the purpose for which scripture is written. In what follows, it is assumed that the Bible is not a philosophy text that was written to address metaphysical questions like, ‘What is the nature of a human being?’, ‘Does the soul exist?’, or ‘Is physicalism true?’, but was authored for the most part as a narrative about the history of the people of Israel.

It would, however, be a mistake to conclude that the Bible, because it is not a philosophical text that is written to address the nature of a human being, says nothing about that nature. In light of the scriptural evidence cited in the next section in which souls are considered to exist separately from bodies or to be re-embodied, it is reasonable to maintain the Bible simply assumes/presupposes the truth of substance dualism because substance dualism is the view that people naturally believe (Cooper 2000; Farris 2020: 21–23).

1.2.1 Scriptural support for soul-body dualism

A variety of biblical texts confirms the view that scripture presupposes the natural belief in substance dualism. For example, there is evidence of belief in ghosts of the dead found both in the Hebrew Bible and Christian New Testament. When Saul saw the army of the Philistines, he was afraid and consulted the Witch of Endor whom he asked to bring up from the dead the ghost of the prophet Samuel (1 Sam 28). Saul’s action was in direct violation of the Israelite law not to consult mediums or wizards (Lev 19:31; 20:6; Deut 18:10, 11), a prohibition which on the face of it presupposes the existence of the soul after physical death.

When the disciples of Jesus saw him walking on the sea, they believed they were seeing a ghost (Matt 14:26). In a passage about Jesus’ identity, he asked his disciples ‘Who do people say that I am?’, and he received the response that some thought he was John the Baptist, others believed he was Elijah, while still others thought he was Jeremiah or one of the prophets (Matt 16:13–14). Even Herod, who had John the Baptist beheaded, wondered if Jesus was John (Matt 14:2). The mere suggestion that Jesus might be John the Baptist is interesting because it is reasonable to think the location of John’s body was well known, and it could easily have been verified that his body was still there. What, then, were people, including Herod, thinking? Most plausibly, they thought Jesus was John’s soul re-embodied. The belief of ordinary people in substance dualism also provides the most plausible epistemological backdrop for the conviction of those who knew Jesus that he was casting out unclean spirits from people who were possessed by them (Mark 1:34). And when Jesus stood among his disciples after his resurrection, they were startled and frightened, and supposed they saw a spirit (Luke 24:36–37). As the New Testament scholar Joel B. Green, who rejects substance dualism, writes, ‘It is difficult not to see in the disciples’ responses a [substance] dualist anthropology; accordingly, in their imaginative categories, they were encountering a disembodied spirit, a phantasm’ (Green 2004: 91). Additionally, when Peter arrived at the door of Mary’s house after he had been jailed by Herod, the persons present insisted to a maid, Rhoda, who reported that Peter was at the door, that it could not be Peter but must be his angel (Acts 12:15).

And what about the apostle Paul? A comment of his in his second letter to the Corinthians indicates that he believed in substance dualism. In 2 Cor 12:2–4, he wrote,

I know a person in Christ who fourteen years ago was caught up to the third heaven – whether in the body or out of the body I do not know; God knows. And I know that such a person – whether in the body or out of the body I do not know; God knows – was caught up into Paradise and heard things that are not to be told, that no mortal is permitted to repeat.

The fact that Paul is uncertain about whether this experience was or was not ‘in the body’ makes clear that he believed it was coherent to think that he might have been caught up to the third heaven in a disembodied state (‘out of the body’), which suggests he believed in the existence of the soul and substance dualism. The fact that Paul believed this is not surprising, for two reasons. First, he was largely writing to ordinary human beings, and ordinary human beings believe in substance dualism. Second, Paul was a Pharisee, and as will be made clear below, the Pharisees believed in both the soul’s existence and substance dualism.

The philosopher Kevin Corcoran, who is not a substance dualist, concedes that biblical passages like those cited in the previous two paragraphs support the view that a person is distinct from its body. However, he writes that

to the extent that [such passages] suggest that a person might exist ‘apart from the body,’ it does not follow that the nature of that existence is immaterial or nonbodily […] So, to exist in a state that is ‘away’ from the body does not entail that the state is an immaterial state of an immaterial soul. It could be a bodily state that includes none of the matter that makes up the earthly body. (Corcoran 2006: 145–146)

It would be unreasonable to claim that these texts provide an account of the ontological nature of a self which exists or is capable of existing apart from its physical human body. However, it is reasonable to believe that they presuppose the truth of substance dualism in the broad sense that there are two substances, a physical human body and the self whose body it is, and that the latter is separable from and can exist apart from the former. What a philosopher does is reflect on the natures of the two substances. It is as a result of such reflection that features of the soul, like its simplicity as a substance and complexity in terms of its psychological capacities, are affirmed. But it must be emphasized that while such philosophical reflection enriches our conception of the soul which people like Jesus’ disciples, Herod, and Paul believed is distinct from and can exist apart from a human body or be re-embodied in a different human body, belief in substance dualism is not itself a result of philosophical reflection. The ordinary person naturally believes substance dualism. Thus, it is not surprising to read Corcoran’s recounting of how his mother, upon the death of his father when Corcoran was four, told him that his father was ‘now with God in heaven […M]y mother believed what most Christians have believed down through the centuries, namely, that we human persons are immaterial souls’ (Corcoran 2006: 11, original emphasis).

Anyone who is the least bit familiar with biblical studies will be aware that Christian theologians/philosophers have for two millennia been influenced by the substance-dualist thought of the Greek philosopher Plato (and Platonists more generally). Critics of substance dualism who are also Christians often allege that these theologians/philosophers erroneously read Plato’s ‘Greek’ treatment of substance dualism into the Bible (see Goetz and Taliaferro 2011: Chapter 1 for a detailed description of Plato’s view of the soul, which includes the claims that the soul is immortal [it never came into and will never go out of existence], uncreated, and will, if all goes well for it, survive death forever disembodied). These critics apparently believe that, had these theologians/philosophers not read Plato, they (the theologians/philosophers) would not have found a belief in substance dualism in the Bible, as if to suggest that Plato was the first person to come up with the idea of substance dualism. For example, the theologian Alister McGrath writes that ‘[t]he notion of an immaterial soul was a secular Greek concept, not a biblical notion […] The biblical vision of humanity was that of a single entity, an inseparable psychosomatic unit with many facets or aspects’ (McGrath 2015: 137–138). The New Testament scholar Joel B. Green writes about the post-resurrection appearance of Jesus to his disciples (Luke 24: 36–37) mentioned above that ‘we find no witness to resurrection as escape from bodily existence (as one would expect if a Platonic dualism were presumed here)’ (Green 2004: 92). Green goes on to claim that ‘Jesus [is not] an “immortal soul” free from bodily existence’ and that ‘[r]esurrection is not soul-flight’ (Green 2004: 92, 93). Green’s statements reflect his purpose of showing

that […] an anthropology that posits an ontologically distinct soul, which constitutes the ‘real person’ and which guarantees survival of personal identity from this life to the next, is not only unnecessary but actually stands in tension with key aspects of the resurrection message of the Scriptures. (Green 2004: 86)

Green seemingly believes that, because Jesus possessed a resurrection body, as opposed to being disembodied after death, he (Jesus) was not a soul and substance dualism is false. However, substance dualism per se implies nothing about whether the afterlife will be an embodied (as Christians believe) or disembodied (as Plato thought) existence. Substance dualism is no more, but no less, than the anthropological view that there is a soul which is ontologically distinct from its body, and this view can be true whether the soul is or is not embodied in the afterlife (or is or is not immortal or uncreated). In other words, substance dualism is not, as Green (and McGrath) seems to think, synonymous with Platonic substance dualism. One can believe in the former without believing in the latter. Those concerned about the influence of Platonic dualism on Christian thought seemingly overlook or forget the distinction between an ordinary belief in substance dualism and a philosophical development/treatment of that belief. Because a belief in substance dualism is commonsensical it is found at all points in time and space on the planet earth (e.g. it is found in Hinduism and Buddhism). While Plato philosophized about substance dualism, he did not come up with the idea. Therefore, if one rejects certain aspects of Platonic thought about the soul, one does not undermine the truth of substance dualism per se or the integrity of the biblical authors’ presupposition of it.

N. T. Wright is another biblical scholar who questions the belief in substance dualism in the New Testament (Wright 2016). He emphasizes that the New Testament does not concern itself with philosophical anthropology, and argues that when the New Testament authors do talk about the soul (psyche), it is not as an entity that is distinct from its physical body but as something like the Hebrew nephesh, which he believes is the living, breathing, creature with bodily and psychological properties (the view frequently referred to as Hebrew monism and a version of property dualism, for which see section 3.1). Wright claims that many Christians are unaware of this Hebrew anthropology because they have been influenced, if not blinded, by Greek substance dualism, particularly in its Platonic form where the soul exists disembodied forever after death.

What might a substance dualist say in response to Wright? First, it does not follow from the fact that the New Testament does not concern itself with philosophical anthropology that its authors, who were for the most part Jewish, embraced a Hebrew monistic view of a human being. The Hebrew Bible is no more concerned with philosophical anthropology than is the New Testament. To maintain that it teaches, presupposes, or implies a monistic understanding of a human being runs up against the fact that ordinary people, whether Jewish or non-Jewish, are substance dualists. We get a glimpse of the belief in substance dualism in 1 Samuel 28, which was cited above. Moreover, as Wright himself points out,

[a]ny Jew who believed in resurrection, from Daniel to the Pharisees and beyond, naturally believed in an intermediate state in which some kind of personal identity was guaranteed between physical death and the physical re-embodiment of resurrection. (Wright 2003: 164; cf. Cooper 2000: 101–103)

And as Wright points out elsewhere, one must be careful about using linguistic expressions as the basis for asserting what people believe about the nature of the afterlife. Wright makes clear that just as it is possible to use language about the soul and life after death to refer to the idea of physical resurrection, so also it is possible to use language about physical resurrection to refer to the idea of the soul and life after death. Thus, it is erroneous to conclude from the fact that the Pharisees are consistently described in the Gospels and the Acts of the Apostles and extra-biblical sources as believing in the resurrection of the dead that they did not believe in the existence of the soul that would receive a new body in the future. They did believe in the soul’s existence and its future re-embodiment, as Wright himself notes with the support of various texts (Wright 1992: 320–34).

Second, it should not be forgotten that the apostle Paul was a Pharisee. That he believed, like other Pharisees, in the possibility of disembodiment is evidenced in 2 Cor 12:1–4, which was cited above. Wright says the following about this passage:

[Paul] never suggests that, if he wasn’t embodied, it was his psyche which made the journey [to the third heaven]. The fact that he is uncertain about whether this experience was or wasn’t ‘in the body’ indicates that, for him, it wouldn’t have been problematic if the body had been involved. For him, the body could just as well have been carried up to heaven […] Equally, of course, that fact that he can consider the possibility that the experience might not have been ‘in the body’ does indeed indicate that he can contemplate non-bodily experiences, but […] I don’t think one can straightforwardly argue from this to what is now meant, in philosophical circles, by ‘dualism’. (Wright 2016: 6–7, original emphasis)

A substance dualist will likely respond that one need not argue from this passage to substance dualism. The fact that Paul can ‘indeed contemplate non-bodily experiences’, experiences had without a body, indicates that he presupposes commonsensical substance dualism. Wright seems to believe that the ‘dualism’ of philosophical circles is Platonic in form. One certainly cannot, as Wright says, straightforwardly argue from what Paul says in 2 Cor 12:1–4 to the conclusion that he believed in Platonic dualism. But, again, substance dualism and Platonic dualism are not the same thing. The latter is a species of the former, and a rejection of the species is not sufficient for a rejection of the genus.

The criticisms of biblical scholars and theologians of substance dualism examined in this sub-section reflect a belief held by many professional philosophers and scientists that substance dualism is false. The explanations given for this belief are typically that developments in neuroscience and the methodology of science as a whole support the falsity of substance dualism (see Theology and Neuroscience). Section 2 is concerned with these issues.

2 Causal interactionism and science

2.1 Mental-physical correlations

Does modern science give rise to problems for a belief in the soul and substance dualism? According to some individuals, what goes on in disciplines such as neuroscience provides evidence that the soul does not exist. For example, the contemporary philosopher Nancey Murphy thinks that neuroscientific localization discoveries (that reveal the correlation between capacities for language, sight, and emotion and specific regions of the brain) support the belief that the subject of those capacities is the brain itself and not a soul that is ontologically distinct from its brain. Murphy writes that

[a] major part of current neuroscience research involves mapping regions of the brain (neuroanatomy) and studying the functions of the various regions (neurophysiology). Studies of this sort intersect in fascinating ways, the philosophical issues [concerning the relationship between the mind and brain]. First they provide dramatic evidence for physicalism. As neuroscientists associate more and more of the faculties once attributed to mind or soul with the functioning of specific regions or systems of the brain it becomes more and more appealing to say that it is in fact the brain that performs these functions. (Murphy 1998: 13)

According to Malcolm Jeeves, ‘[t]he nature of the [causal] interdependence increasingly uncovered by scientific research makes a substance dualism harder to maintain without tortuous and convoluted reasoning’ (Jeeves 2004: 240).

Is Jeeves correct? Despite what Murphy writes about the dramatic evidence that research in neuroscience provides for physicalism, she believes someone like Jeeves overstates the case against substance dualism. Murphy writes that

[i]t is important to note that this evidence [from neuroanatomy and neurophysiology] will never amount to proof: it will always be possible for the [substance] dualist to claim that these [mental] functions belong to the mind and that mental events are merely correlated with events in particular regions of the brain. (Murphy 1998: 13)

Murphy understands that the discovery of correlations between mental capacities and events with physical structures and events is not in and of itself sufficient to justify an affirmation of their identity. C. Stephen Evans not only agrees with Murphy’s acknowledgment that correlation is not identity but also wonders why people like Murphy and Jeeves claim it is difficult to believe in substance dualism in light of localization and correlational studies:

What, exactly, is it about these findings that are supposed to create problems for [substance] dualism? Presumably, the mere fact that the mind is causally impacted by the brain is not a problem, since most [substance] dualists have been [causal] interactionists eager to maintain that the body (and indeed the wider physical world), can in some way affect the mind. Is it a problem for [substance] dualism that this causal action takes place through the brain, rather than, say, the heart as Aristotle thought? It is hard to see why this should be a problem. Is it a problem that the causal effects should be the product of specific regions of the brain? Why should the fact that the sources of the effects are localized regions of the brain, rather than the brain as a whole, be a problem for the [substance] dualist? […] We did not need neurophysiology to come to know that a person whose head is bashed in with a club quickly loses his or her ability to think or have any conscious processes. Why should we not think of neurophysiological findings as giving us detailed, precise knowledge of something that human beings have always known, or at least could have known, which is that the mind (at least in this mortal life) requires and depends on a functioning brain? […] [T]hat the mind depends on the body, at least prior to death, is surely not something discovered in the twentieth century. (Evans 2005: 333–334; original emphasis)

2.2 Science and methodological causal closure

If Evans is correct and localization studies present no problem for a belief in substance dualism, is there any reason to think science itself – as opposed to any particular science (e.g. biology, chemistry, physics) – poses a problem for this belief? Some individuals maintain that the methodology of science per se makes it difficult, if not impossible, reasonably to believe in the causal interaction between a soul and its physical body (and, more generally, to believe in the existence of the soul, because the soul’s existence seems superfluous if it cannot causally produce events [e.g. brain events] in the physical world). What science methodologically requires is the assumption of the principle of the causal closure of the physical world (causal closure), which is the principle that the occurrence of physical events can only be explained by the occurrence of other physical events.

2.2.1 Universal versus localized methodological causal closure

What is the reasoning that supposedly supports an affirmation of the methodological causal closure of the physical world? Consider the following comments of the philosopher Jaegwon Kim:

You want [or choose] to raise your arm, and your arm goes up. Presumably, nerve impulses reaching appropriate muscles in your arm made those muscles contract, and that’s how the arm went up. And these nerve signals presumably originated in the activation of certain neurons in your brain. What caused those neurons to fire? We now have a quite detailed understanding of the process that leads to the firing of a neuron, in terms of complex electrochemical processes involving ions in the fluid inside and outside a neuron, differences in voltage across cell membranes, and so forth. All in all we seem to have a pretty good picture of the processes at this microlevel on the basis of the known laws of physics, chemistry, and biology. (Kim 1996: 131–132)

According to Kim, the physical explanatory story is unproblematic until one introduces an immaterial mind (a soul) to explain the raising of one’s arm:

If the immaterial mind is going to cause a neuron to emit a signal (or prevent it from doing so), it must somehow intervene in these electrochemical processes. But how could that happen? At the very interface between the mental and the physical where direct and unmediated mind-body interaction takes place, the nonphysical mind must somehow influence the state of some molecules, perhaps by electrically charging them or nudging them this way or that way. Is this really conceivable? Surely the working neuroscientist does not believe that to have a complete understanding of these complex processes she needs to include in her account the workings of immaterial souls and how they influence the molecular processes involved […] Even if the idea of a soul’s influencing the motion of a molecule […] were coherent, the postulation of such a causal agent would seem neither necessary nor helpful in understanding why and how our limbs move […] Most physicalists [those who believe all of reality is physical in nature…] accept the causal closure of the physical not only as a fundamental metaphysical doctrine but as an indispensable methodological presupposition of the physical sciences […] If the causal closure of the physical domain is to be respected, it seems prima facie that mental causation must be ruled out. (Kim 1996: 132, 147–148)

A believer in substance dualism and soul-to-body causal interaction (i.e. an ordinary person) will express surprise at Kim’s remark that reference to a soul seems neither necessary nor helpful in understanding why and how our limbs move on certain occasions. Surely if, as the substance dualist believes, the soul is what chooses to act for purposes, then reference to it seems absolutely necessary and helpful for understanding why certain movements of human bodies occur. For example, when an author chooses to accept an invitation to write an entry for an encyclopaedia and proceeds to move his fingers in specific ways on a keyboard to type the entry, his purpose for writing the entry teleologically explains (see section 1.1) that choice and the subsequent finger movements which he, as a soul, causally produces for the fulfilment of that purpose.

What, then, might the substance dualist say in response to Kim’s argument that a neuroscientist must, in accordance with the methodological principle of causal closure, exclude any appeal to souls to explain physical bodily movements? The substance dualist can draw a distinction between a neuroscientist as an ordinary human being and a neuroscientist as a physical scientist. Given this distinction, the substance dualist can maintain that a neuroscientist as an ordinary human being can invoke a purpose to explain the relevant movements of an author’s fingers in writing an encyclopaedia entry where those movements are ultimately caused by a soul acting for that purpose. And invoking this explanation is thoroughly consistent with a neuroscientist’s methodologically excluding in principle such explanations in the context of his work as a neuroscientist.

How can the distinction between a neuroscientist (or any scientist) as an ordinary human being and as a scientist be justified? To begin to answer this question, consider the following statement from the pen of the twentieth-century British geneticist, J. B. S. Haldane: ‘when I set up an experiment I assume that no god, angel, or devil is going to interfere with its course’ (quoted in Subramanian 2020: 9). Two points are relevant. First, were Haldane to have believed that the mental-to-physical causation involved in soul-body causal interaction was in principle impossible (inconceivable, as Kim claims), then he would not have needed to make the stated assumption (which concedes the possibility of soul-body causal interaction but excludes it in experimental scientific work). Second, it is possible to distinguish between local and universal causal closure. While a scientist must assume the causal closure of the physical world, he does so only in the limited context of his experimental work. He need not assume that the physical world is closed at all points in time and space. In other words, while Haldane, in trying to ascertain how physical objects causally interact, was justified in assuming that no god, angel, devil, or soul was interfering with that part of the physical world with which he was concerned in his experimental work, this limited assumption in no way required the broader assumption that the entire physical world was closed at every point in space and every point in time.

The substance dualist will make clear that proponents of the argument from causal closure regularly fail to make this local-universal distinction. For example, when the philosopher John Heil presents the methodological argument from causal closure against soul-body causal interaction he assumes that the closure required must be universal in scope: ‘Modern science is premised on the assumption that the material universe is a causally closed system: every event in the material universe is caused by some other material event (if it is caused by any event)’ (Heil 2020: 25, original emphasis). But why think modern science is methodologically premised on the assumption that the material universe in its entirety is a causally closed system?

But, Heil might retort, if a scientist needs to assume limited causal closure, why not think it is reasonable to view this assumption as shorthand for a requisite assumption that is universal in scope? In other words, why not think the argumentative burden is on the substance dualist to explain why the assumption of limited causal closure is not an abbreviation of that which is most general in nature?

At this point, the substance dualist will likely respond that the explanation for why it is not reasonable to understand the assumption of limited causal closure as shorthand for what is universal in nature is because we are aware of reasoning and choosing to act for purposes, where these mental events seemingly produce effects in the physical world (thus falsifying universal causal closure). Given this is the case, it is reasonable to seek to understand how what happens in our mental lives with their physical effects is compatible with the methodology of science. The distinction between limited as opposed to universal causal closure achieves this compatibility.

Given that the assumption of limited, and not universal, causal closure can be methodologically justified, what is it that a physical scientist is attempting to discover about physical objects in his experimental work? In the case of Kim’s neuroscientist, she is attempting to discover the capacities of particles or micro-entities such as neurons to be causally affected by exercised causal capacities of other physical entities, including other neurons. For example, in his pioneering studies of the brain, the brain scientist Wilder Penfield caused movements of limbs of his patients by stimulating the cortical motor areas of their brains with an electrode (Penfield 1975). As Penfield observed the neural impulses caused by the stimulation from the electrode, he had to assume that during his experiments the areas of the brains of his patients were causally closed to other causal influences. Without this methodological assumption, Penfield could not reasonably conclude that it was both (i) the electrode, as opposed to something behind the scene and empirically undetectable such as the soul of the patient or someone else or, in Haldane’s words, a ‘god, angel, or devil’, that was causally affecting the capacities of the neurons to conduct electrical impulses, and (ii) the causal impulses of those neurons that causally affected the same capacities of other neurons further down the causal chain, which resulted in the movements of the limbs. However, there was no reason for Penfield to think that, because his scientific work required the methodological assumption of causal closure in the areas of the brain and body which he was investigating during his experiments, that he also had to be committed, as a scientist, to the assumption that the material universe is universally causally closed so that at other times (times when he was not conducting his scientific work) the relevant brain (neural) events could only be caused by other physical events and not by the soul of the patient (or some other being).

In other words, it does not follow from the fact that, because Penfield or other neuroscientists must methodologically assume causal closure of a delimited area of the brain (body) in the context of their experimental work in order to ascertain how physical entities causally interact, they must be committed as scientists to the universal explanatory exclusion of mental events of souls that on certain occasions cause the occurrence of neural events in their brains. If neuroscientists assume universal causal closure, they do not do so as scientists but as individuals with an independent philosophical commitment which excludes the causal efficacy of souls.

If the foregoing reasoning is sound, then scientists can reasonably remain ordinary human beings who are open to the causal efficacy of souls on brains on certain occasions. But on which occasions? The obvious answer is, as has already been suggested, on occasions when souls are reasoning and purposefully choosing to act and carrying out their choices. The purposeful typing of an encyclopaedia entry is an example of one such occasion (as is the occasion when Penfield purposefully stimulated a patient’s brain with an electrode). It is reasonable for a writer to assume that when he chooses to type his entry and his fingers move in accordance with the purpose for which he is typing that his choice (or some other mental event correlated with his choice) is directly causing the relevant brain (neural) events and indirectly producing the movements of his fingers that are effects of those brain events. It is unreasonable to think that every time an author purposefully chooses to type an encyclopaedia entry, or do anything else, physical causes alone purposelessly occur to produce the very movements of his fingers that are required to type his written work. Such a coincidence would truly be miraculous.

However, what if there are sometimes undetermined (uncaused) events in micro-entities? What if on occasion a neuron fires without any cause whatsoever? If it is assumed that neurons occasionally do fire in this way, is it possible to distinguish between those firings that occur without any physical cause and those that occur as the result of being causally determined solely by a mental event in a soul? After all, the two firings are alike to the extent that both lack a physical cause. Do they differ in a relevant way?

It is possible to distinguish between these two firings by remembering that the relevant mental causal event in a soul is an action (or a mental event correlated with that action) that has an explanation in the form of a purpose. How plausible is it to maintain that every time a soul makes a choice to write for a purpose that the relevant uncaused neural events which lead to the purposefully chosen finger movements just happen to occur without any cause? Such repeated coincidences would again be miraculous. It is far more reasonable to maintain that, while those neural firings lack any physical cause, they are caused by the relevant purposeful mental event.

2.2.2 An alleged problem for soul-body causal interaction

Soul-to-body causal interaction requires the occurrence of physical events that lack physical causes. It is therefore important to emphasize that the belief in the soul’s existence and causal activity is not the result of a failure to find a physical cause for a physical event (e.g. a neural firing). That is, the belief in the existence of the soul and its causal activity is not arrived at in light of a failure to find a physical cause for the relevant physical event. That would be an appeal to a soul-of-the-gaps explanation. The situation is the reverse. On the occasions when a person is aware of choosing purposefully to perform an action, such as writing an encyclopaedia entry, it must be the case (absent ‘miraculous’ coincidences) that there is some initial physical event (neural firing) which is not caused by another physical event but by a mental event which has a purposeful explanation. In other words, it is not that gaps in the physical causal story lead to belief in the soul, but that belief in the soul and purposeful mental causes leads to the belief that there must be gaps in the physical causal story.

2.2.3 A hierarchical/layered view of reality and methodological causal closure

According to the philosopher John Heil,

[t]he universe contains levels or layers of objects and properties governed by successive levels of causal laws. Although objects at higher levels are often enough made up of objects at lower levels, it is nevertheless true that higher-level objects and their properties have lives of their own. They are not reducible to, not ‘nothing but’, arrangements of objects and properties at lower levels. (Heil 2020: 123)

Heil maintains that laws at the higher levels hold only ceteris paribus or ‘other things being equal’. For example, assume it is a law that if a soul, S, wants x and believes y is needed to obtain x, then S wants and will act to obtain y. Thus, if S desires to take the subway and believes a ticket is necessary to do so, then S will want and act to obtain a ticket. S will want and act to obtain a ticket, says Heil, unless S believes he has no money, which might lead to his losing his desire to ride the subway, or S is hit by a piece of falling plaster and knocked unconscious, etc. According to Heil, the laws of biology and chemistry – though lower in the hierarchy of laws than psychological laws – are similar to those found in psychology in the sense that they are ceteris paribus in nature. However, writes Heil, ‘[t]he laws governing the basic entities [the lowest-level laws] studied in physics […] are exceptionless [non-ceteris paribus]’ (Heil 2020: 123).

What Heil never explains is why the lowest-level laws are (must be) exceptionless. Why could they not be ceteris paribus in nature, such that physical event y will occur under condition C given the occurrence of physical event x, unless some other event such as a choice by soul S for a purpose intervenes to prevent the occurrence of y? Why think a soul could not intervene in this way? After all, a soul is, by hypothesis, a simple entity with capacities. As a simple entity, it is ontologically akin to the lowest-level physical entities with their capacities. Does science’s methodological commitment to the causal closure of the physical world exclude causal intervention by a soul at the level of basic entities? If the argument of section 2.2.1 is sound, then the answer is ‘no’. The causal closure (as opposed to the methodological assumption of the causal closure) of the physical world? If Heil were to respond that the physical world is causally closed, then one could ask what justifies the claim that this is the case. In lieu of an answer, Heil might simply assert that he has no reason for believing that the physical world is causally closed. He just believes that it is. There is nothing in principle philosophically suspect about a person having a belief that is not justified in terms of one or more other beliefs. All of us have beliefs of this kind, what philosophers think of as basic beliefs. Basic beliefs are not uncaused or freely chosen. For example, a basic belief that the stove top is hot might be caused by an awareness of the heat one experiences while standing before the stove. Similarly, a basic belief that one is happy might be caused by one’s awareness of one’s experiences of pleasure. Were Heil to maintain that his awareness of the physical world or some property of the physical world causes him to believe the physical world is causally closed, then he would have a basic belief that is not shared by the substance dualist. At this point, there would be no epistemic higher court of appeal. There would be an irresolvable difference in basic beliefs.

2.2.4 The non-spatiality of the soul and methodological causal closure

In the history of thought about the soul, the issue of its location has received serious attention. Is the soul located in space? It certainly seems that it is. For example, René Descartes wrote that ‘I imagined [the soul] to be something tenuous, like a wind or fire or ether, which permeated my more solid parts’ (Descartes 1984: 17). Philosophers writing about the nature of the soul, like Augustine and Aquinas, affirmed that the soul is present in its entirety in every point of space occupied by its physical body because, as Descartes’ comment suggests, it seems to us that we fill the space occupied by our physical body (see Goetz and Taliaferro 2011: 43–45, 51–53). However, Descartes, for reasons that need not be reviewed here, apparently denied that the soul is present in space at all (see Goetz and Taliaferro 2011: 70–76).

When one reads philosophical treatments of substance dualism, one regularly encounters the objection that it is unintelligible how a non-spatial substance can causally interact with one that is spatial (see Sosa 1984; Kim 1996; Taylor 1992). However, what should be remembered is that the objection to substance dualism from methodological causal closure essentially has nothing to do with whether a soul is spatially located. Even if a soul is located in space (say, in the space of its physical body), the objection from methodological causal closure is that there is no explanatory room for mental causes of physical events, even when the mental events involved in those causal explanations occur in spatially localized souls.

3 From where does the soul come?

3.1 Emergentism

While there are various answers to the question about the soul’s origin, within the Christian tradition it has often been claimed (e.g. Augustine, Aquinas, and Descartes) that the human soul, like every other fundamental constituent of reality, is directly created by God out of nothing (ex nihilo; see Goetz and Taliaferro 2011). Some have claimed that the development of science poses special problems for this view. For example, the philosopher Timothy O’Connor, a Christian theist who does not believe in the truth of substance dualism, maintains that

[t]he fundamental problem [with the idea that God creates a human soul ex nihilo] is that our sciences point to highly continuous processes of increasing complexity, but the two-substance account [substance dualism] requires the supposition of abrupt discontinuity. The coming to be at a particular point in time of a new substance with a suite of novel psychological capacities […] would be a highly discontinuous development [in the physical world]. (O’Connor 2013, original emphasis)

What does O’Connor propose as an alternative to creation ex nihilo of the soul? He claims that at some point in the continuous biological story, psychological/conscious capacities – which are fundamentally different in kind from physical/non-conscious capacities – emerged from the hierarchically-structured physico-chemical properties of the brain. According to O’Connor, ‘[t]hese conscious states have distinctive intrinsic features, immediately apprehended by their subject, that in no way resemble the sorts of features science attributes to complex neural states’ (O’Connor 2013).

Is O’Connor’s suggestion about mental capacities causally emerging from physico-chemical properties of the brain – what might be called emergentist property dualism – explanatorily superior to the substance dualist account which maintains that God provides a human physical body with a soul created ex nihilo? In response to O’Connor, the substance dualist will likely respond that, if substance dualism is objectionable for the reason that it introduces an abrupt discontinuity into the developmental processes in the natural (physical) world, then O’Connor’s emergentist view is no less objectionable for the same reason. After all, O’Connor recognizes the reality of emergent psychological/conscious capacities which, because of their being different in kind from physico-chemical properties of the brain, are just as discontinuous with events and properties of the physical world as a soul that is created ex nihilo by God. And the substance dualist will likely add that substance dualism has the advantage that it is an affirmation of the ordinary person’s view that the distinctive intrinsic psychological features whose reality is acknowledged by O’Connor are the properties of souls.

O’Connor’s emergentist view is an instance of what in philosophy is termed property dualism or a dual-aspect view of the mind. According to property dualism, there is one substance which has two kinds of properties (capacities) – psychological and physical – which are conceptually and ontologically distinct from each other. The more basic properties are physical and these give rise to the less basic psychological properties. For present purposes, what is important to make clear is that if the methodological argument from causal closure is successful against substance dualism and its appeal to mental events to explain the occurrences of certain physical events, then that argument is equally successful against property dualism. This is because property dualists, like substance dualists, affirm that mental events explained by purposes explain the occurrences of some physical events in this world (see O’Connor 2002). If the methodological argument from causal closure excludes any appeal to mental events to explain the occurrences of physical events, then property dualism is subject to the same explanatory irrelevance as substance dualism.

Emergentism can be thought of as a dualist genus of which property dualism is one species. Another species of emergentism comes in the form of substance dualism. According to William Hasker, who is a defender of emergentist substance dualism, when a brain and/or central nervous system becomes sufficiently developed it generates

not merely mental properties and experiences, and not merely new causal powers, but a new individual, a subject that has those experiences and exercises […the] causal powers […T]he new individual is an emergent immaterial entity, an ‘emergent self’ […T]his new individual is beginning to sound quite a bit like the soul posited by creationist versions of dualism [creationist substance dualism]; there are, however, some important differences. The emergent self is generated by the organic body through a natural process, rather than being inserted into the body from outside […T]he postulation of such a soul makes this view a version of dualism; indeed of substance dualism and not of mere property dualism. Hence the name given to the view: emergent dualism. (Hasker 2015: 159–160, original emphasis)

Hasker believes emergent dualism ‘can well be viewed as a contemporary version of traducianism’, which is ‘the view that a person’s soul is somehow derived from her parents, as a result of the natural process of reproduction’ (Hasker 2015: 152), and is superior to creationist substance dualism because the latter

is difficult to reconcile with any plausible version of evolutionary biology. Evolution presents us with a very long and complex story in which […] the most primitive life-forms gave rise through a natural process to the complex kinds of life we observe today, including human life. The question is, how do the divinely created souls fit into this story? More complex animals, with greater cognitive powers, require ‘higher,’ more powerful souls; a highly developed brain is useless to an animal if the animal’s soul is unable to utilize it effectively […] Perhaps we might suppose that God simultaneously brings about a change in the genetic mechanism (DNA and so on), and also supplies a new, more powerful soul to take advantage of the improved cognitive hardware. But this would not by any means be evolution as a natural process, and we can confidently predict that it would be rejected by evolutionary biologists, theists, and atheists alike. The truth is that creationism concerning the soul does not fit at all comfortably with an evolutionary account of life. This fact creates a significant burden for creationism, though one of which its proponents have often seemed to be unaware. (Hasker 2015: 155, original emphasis)

What, if anything, might a creationist substance dualist say in response to Hasker? What Hasker himself thinks of the principle of causal closure (see section 2.2) provides the basis for a possible response. Hasker points out that ‘physicalists uniformly insist on the causal closure of the physical domain [the physical world], which means in effect that any event that has a cause at all has a sufficient physical cause’ (Hasker 2015: 157, original emphasis), where a sufficient physical cause is a physical cause that completely explains the occurrence of an event in the physical world that has a cause. Hasker adds that

[t]his [physicalist] view […] has consequences that are truly mind-boggling. For instance, it means that one never in fact performs an action because one consciously decided to perform it; rather, both the physical action and the decision to perform the action are entirely the result of physical brain-states, states over which one has no conscious control whatsoever […This is] one more example of the unfortunate consequences of the doctrine of causal closure […To] insist that because of the occurrence of conscious mental events things go differently [in the physical world] than they would go in the absence of such events […] upsets much of the thinking that underlies contemporary naturalism concerning the human person. (Hasker 2015: 157–158, original emphasis)

However, given that Hasker is willing to upset the thinking about causal closure that underlies contemporary naturalism concerning the explanations of a human person’s action, why does he think a creationist substance dualist should be unwilling to upset that thinking and insist that God cannot causally intervene in the evolutionary process (in which a variety of complex organisms have descended from a common ancestor) at one or more points? It is true, as Hasker writes, that the creationist substance dualist account in which God causes a physical change in an organism to accommodate the creation of a soul that is suitable for that organism is not consistent with the idea of evolution as a causally closed natural process. But given Hasker’s own insistence on the need for and reality of psychological explanations to account adequately for certain instances of human physical behaviour, where these explanations entail the falsity of the causal closure of the physical world, what is problematic with the idea that God occasionally purposefully causally intervenes in the evolutionary causal story (see Theology and Evolution)?

Hasker raises a further concern about the creationist substance dualist’s account of the origin of a soul. He believes that, if God creates a human soul ex nihilo, then the creationist substance dualist cannot draw a line in a principled way between what does and does not have a soul. Given the obvious fact that sub-human animals have sensations and, perhaps, other conscious experiences,

the creationist is forced to attribute divinely created souls to animals—not necessarily souls in every respect equivalent to human souls, but souls that are adequate to the sort of thoughts and experiences the animals do seem to have. But now a problem arises: how far do we carry this? How far down the ‘scale of life’ do we find these divinely-created souls? Of course, it is difficult for anyone to say with confidence just which simpler life-forms have conscious experience, and which do not. The problem, however, is that any answer the creationist can give tends to be embarrassing to his view […I]f we are generous in assigning souls to lower life-forms […] we have the unappealing notion of God’s creating souls by the billions for spiders, mosquitoes, and intestinal parasites. And then there is the problem of what becomes of all those souls when the creatures perish. (Hasker 2015: 154)

Once again, it is fair to ask what a creationist substance dualist might say in response to Hasker. Perhaps the creationist substance dualist can look one more time to Hasker for help. Does he believe the brains/nervous systems of spiders and mosquitoes generate suitable souls for those creatures? He seemingly does believe this, because when he discusses the ability of the freshwater polyp, the hydra, to regenerate itself when cut into pieces he claims that ‘when a new organism is produced’, a new soul is generated by the organism ‘as a matter of course’ (Hasker 2005: 99). So, on emergent dualism, the existence of generated souls seems to go a significant distance down the scale of biological life. A creationist substance dualist will likely wonder, and reasonably so, why the biological generation by the billions of souls for spiders, mosquitoes, and freshwater polyps is so much more appealing than the unappealing notion of God’s creating souls for these organisms ex nihilo. And, given the existence of these billions of souls on emergent dualism, it is now reasonable to ask whether they cease to exist at death or God preserves them in existence after death in the same way that Hasker says God preserves human souls in existence after death (Hasker 2015: 160–161). If Hasker is not embarrassed by a proliferation of souls on emergent dualism and concerns about what happens to them after death, a creationist substance dualist will likely wonder, and reasonably so, why he should be embarrassed by a proliferation of souls on creationism and what happens to them after death.

3.2 Panpsychism

Some people reject both emergentist property dualism and emergentist substance dualism because both views affirm that what is completely physical gives rise to what is psychological, which violates the causal principle that something cannot come out of nothing (out of nothing comes nothing or ex nihilo nihil fit). According to the theologian Joanna Leidenhag, an ontological jump in which something comes out of nothing ‘warrants the pejorative adjectives of being “brute” or “magic”’ (Leidenhag 2021: 82). People who reject the property and substance dualist forms of emergentist dualism and creationist substance dualism, but who also believe in the reality of both the physical and the psychological, must look to affirm some other form of dualism. One such form is panpsychism. Panpsychism maintains that fundamental reality has both physical and psychological properties, and the psychological lives of macro human beings are explicable in terms of the micro psychological properties of fundamental reality. Leidenhag maintains that the most promising panpsychist explanation here is emergentist in nature but nevertheless acceptable because the macro psychological/mental is explained in terms of the micro psychological. There is emergence ‘from mental parts to mental wholes’ (Leidenhag 2021: 79). How this happens is not at present understood, ‘but it is not a deep metaphysical mystery of the same kind that brute emergence [from the physical to the mental] seems to be’ (Leidenhag 2021: 81).

Leidenhag claims that one issue that makes the panpsychist’s challenge of accounting for the psychological nature of human beings especially difficult is

The Combination Problem: How do the experiences at the fundamental physical level combine to yield the experiences humans typically enjoy? […] Much ink has been spilt on the combination problem in the contemporary literature surrounding panpsychism […] because it represents the greatest gap in the panpsychist’s account of human consciousness. (Leidenhag 2021: 71, 72)

Why is combinatorial explanation especially problematic? At this point, the issue of the soul’s simplicity comes front and centre. As substance dualists repeatedly have made clear (see Goetz and Taliaferro 2011), the mind, while it has a multiplicity of psychological capacities (see section 1.1), seems not to be composed of parts. Thus, writes Leidenhag,

[t]he idea that [multiple] minds are just not the sort of things that can combine [into a single mind] boils down to an intuition, but it is one that many philosophers find highly compelling. (Leidenhag 2021: 72)

Can the combination problem be overcome? Leidenhag writes that

[t]he combination problem itself is ‘significant but not insurmountable’ and remains a weakness in the panpsychists’ account of consciousness but it is not a deep metaphysical mystery of the same kind that brute emergence seems to be and does not land a fatal blow. (Leidenhag 2021: 81)

A substance dualist will likely disagree with Leidenhag’s optimism, because the combination problem runs up against a conceptual incoherence, namely, explaining the existence of the mind which has no parts in terms of parts. Moreover, a creationist substance dualist will likely ask a panpsychist what is problematic about creationist substance dualism. Leidenhag believes creationist substance dualism

has given rise to a problematic ontological divide between humanity and other creatures, which sits uncomfortably with the theory of evolution. It also gives the soul and the body two radically different origin stories […] Furthermore, there remains a lingering dissatisfaction in employing divine action as an explanation for a widespread and systemic feature of the universe [the origin of the human mind] before all other possibilities have been exhausted. (Leidenhag 2021: 84)

A creationist substance dualist will probably respond that the theory of evolution is concerned with the explanation of the existence of physical organisms, period. Whether the mind is a physical organism is a philosophical, not a scientific, issue. If the theory of evolution is ensconced in naturalism, then the explanatory efficacy of the mind is excluded from the outset. At this point, a creationist substance dualist will rehearse the arguments that were set forth in section 3.1 in response to O’Connor’s and Hasker’s objections from evolutionary theory against creationist substance dualism. And a substance dualist will likely add that the appeal to divine mental action to explain certain events in the physical world is no more dissatisfying than the appeal to the mental action of human souls to explain certain events in the physical world (see sections 2.2.1 and 3.1).

The creationist substance dualist recognizes that a soul is contingently related to its physical body. Because of this contingent relationship, a soul not only might have had a different physical body but also might have existed disembodied. Why, then, does a soul have a physical body? As Leidenhag points out, ‘substance dualists can offer little explanation from within the natural order as to why this might be the case’ (Leidenhag 2021: 70). A creationist substance dualist will not disagree but insist that an explanation can be sought and found outside the natural order in terms of the purpose of life.

4 The soul and the end of life

4.1 The soul and the purpose of life

If it is assumed for the sake of discussion that the soul is created for a purpose, what might that purpose be? Those within the Christian tradition have generally agreed that the answer to this question is the experience of perfect happiness, where the meaning of the word ‘perfect’ is often either taken for granted, replaced with words like ‘blessed’ or ‘eternal’, or implied by such terms as ‘beatitude’ or ‘felicity’. Thus, in the early middle ages, Saint Augustine (354–430) wrote that ‘[w]e wish to be happy, do we not? […] Everyone who possesses what he wants is happy […] Therefore […] whoever possesses God is happy’ (Augustine of Hippo 2008: 52–53). Not too many years after Augustine, Boethius (480–524) wrote The Consolation of Philosophy in which his interlocutor Lady Philosophy reminded him that

[t]he whole concern of men, which the effort of a multitude of pursuits keeps busy, moves by different roads, yet strives to arrive at one and the same end, that of happiness […] In all of these things it is obviously happiness alone that is desired; for whatever a man seeks above all else, that he reckons the highest good. But we have defined the highest good as happiness; wherefore each man judges that state to be happy which he desires above all others. (Boethius 1973: 233, 235)

And a few centuries later, Saint Anselm (1033–1109) affirmed that God created and sustains human beings in existence us for the purpose that they be happy: ‘Man […] was created […] for the purpose of eternal happiness’ (Anselm of Canterbury 1998: 316). Thomas Aquinas (1224/25–1274) agreed with Augustine, Boethius, and Anselm: ‘the ultimate end of man […] is called felicity or happiness, because this is what every intellectual substance desires as an ultimate end, and for its own sake alone’ (Aquinas 1975: 102). John Calvin (1509–1564) also believed that humans were created for the purpose that we be perfectly happy. According to him, in order that God ‘may encourage us in every way, he promises present blessings, as well as eternal felicity, to the obedience of those who shall have kept his commands’ (Calvin 2008: II. 8. 4). Indeed, because the ‘holy patriarchs expected a happy life from the hand of God (and it is indubitable that they did), they viewed and contemplated a different happiness from that of a terrestrial life’ (Calvin 2008: II. 10. 13). More recently, C. S. Lewis added his voice to the vast weight of the Christian tradition when he affirmed that the purpose for which God created human beings is that they be ultimately or finally perfectly happy. In his book The Great Divorce, which is about a fantastical bus trip from hell to heaven, Lewis had one of the ghostly heavenly visitors say ‘I wish I’d never been born […] What are we born for?’, to which a spirit answers, ‘[f]or infinite happiness’ (Lewis 2001: 61). Lewis wrote elsewhere that infinite, complete, or ecstatic happiness is the life of the blessed and he stated that we must suppose ‘the life of the blessed to be an end in itself, indeed The End’ (Lewis 1992: 92).

‘But’, one might ask, ‘what is happiness?’ There is disagreement among those who agree about the purpose of life as to how to answer this question. However, they all agree that perfect happiness cannot be had in this life. Its attainment requires the survival of death. Here, the existence of the soul takes on additional importance.

4.2 The soul and the possibility of life after death

All of the theologians/philosophers quoted in section 4.1 believed fulfilment of the purpose of life requires the survival of death. What is required for the survival beyond death? The survival of the earthly human body? If that is required, most people think the prospects for the survival beyond death are extremely bleak, if not non-existent. This is because of the obvious fact that the human body is destined for decomposition and ultimate extinction after death. Hence, it has seemed readily apparent to most individuals that if there is any hope for life after death and the fulfilment of the purpose of life, then the existence of the soul is required. It is required, at least in part, because the soul is (as mentioned in sections 1.1.2 and 3.2) a simple entity in the sense that it is not made of, and thus is not decomposable into, parts. Hence, it cannot suffer the fate of its physical body. Within the Christian tradition, it is believed that the soul’s continued existence after death requires the sustaining creative activity of God. But, if God created the soul for the purpose that it experience perfect happiness, then it makes sense to maintain that God will do what is necessary and sustain the human soul in existence post-mortem so that it has the possibility of experiencing the perfect happiness for which it was created.

Though the soul exists in this life and must survive death in order to experience the perfect happiness for which it is created, why does it have a body in this and the resurrected life? In light of its purpose for existing, substance dualists believe a plausible answer is that the soul has a body in this life and the life to come because God has chosen to make the body a source of the soul’s happiness.

4.3 Abortion

There is, then, an intuitive link between the fulfilment of the purpose of life as perfect happiness and the existence of the soul. But when does God initially create the soul? Can the creationist substance dualist non-arbitrarily specify the point at which God brings the soul into existence? Is it at conception? When the foetus is conscious for the first time, which is likely between eight to twelve weeks after conception? And does substance dualism, which defines a human being as a soul-body compound, entail that abortion is more morally permissible than it is on a position which, say, defines a human being physically in terms of the genetics of a fertilized egg?

Creationist substance dualists will likely respond that their ignorance about when the soul first comes into existence does not automatically make for a more liberal moral position on abortion. For example, they can claim that there are no compelling grounds for claiming that souls must be conscious in order morally to justify prohibiting abortion. So the existence of an unconscious soul at conception can yield the same moral position on abortion as that defended by those who define what it is to be a human in terms of a fertilized ovum. Alternatively, creationist substance dualists might reasonably argue against abortion on the basis of a sanctity-of-life principle, or in terms of the foetus’ potential for ensoulment at some point after conception up to and including birth.

5 Conclusion

Most of the topics in this entry merit much further treatment than that provided here, and discussions of them will undoubtedly continue unabated into the future. It is the hope of the author of this entry that its contents will helpfully contribute to future thought and debate.


Copyright Stewart Goetz (CC BY-NC)


  • Further reading

    • Brown, Warren S., Nancey Murphy, and H. Newton Maloney (eds). 1998. Whatever Happened to the Soul? Minneapolis: Fortress Press.
    • Corcoran, Kevin J. 2006. Rethinking Human Nature: A Christian Materialist Alternative to the Soul. Grand Rapids: Baker Academic.
    • Evans, C. Stephen. 2005. ‘Separable Souls: Dualism, Selfhood, and the Possibility of Life After Death’, Christian Scholars Review 34: 327–340.
    • Farris, Joshua R., and Charles Taliaferro (eds). 2015. The Ashgate Research Companion to Theological Anthropology. Surrey: Ashgate.
    • Goetz, Stewart, and Charles Taliaferro. 2011. A Brief History of the Soul. London: Wiley-Blackwell.
    • Hasker, William. 1999. The Emergent Self. Ithaca, NY: Cornell University Press.
    • Heil, John. 2020. Philosophy of Mind: A Contemporary Introduction. New York: Routledge. 4th edition.
  • Works cited

    • Anselm of Canterbury. 1998. Anselm of Canterbury: The Major Works. Edited by Brian Davies and G. R. Evans. Oxford: Oxford University Press.
    • Aquinas, Thomas. 1975. Summa Contra Gentiles. Translated by Charles J. O’Neill. South Bend: University of Notre Dame Press.
    • Augustine of Hippo. 2008. ‘The Happy Life’, in Happiness: Classic and Contemporary Readings in Philosophy. Edited by Stephen M. Cahn and Christine Vitrano. Oxford: Oxford University Press, 51–60.
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