1 Classical/medieval thought
The earliest Greek philosophers looked for a fundamental material cause underlying all changes in nature. Thales (620–550 BC) identified this as water. Anaximenes (570–500 BC) thought it was air in different states of rarity or density. Anaximander (610–525 BC) believed that none of the basic elements (earth, air, fire, and water) could be the first principle and chose rather an undetermined principle that he called ‘the infinite’. Convinced that all things are constantly changing, Heraclitus (c. 500 BC) named fire as the first principle. All things are ephemeral patterns of continuity in the perpetual flux of fire. Parmenides (c. 500 BC), on the contrary, denied the very possibility of change (Nahm 1964: 31–45, 62–77, 87–97).
Early philosophers also considered the efficient cause. Aristotle notes that Thales ‘seems to have held soul to be a motive force’ (On the Soul I, 2 [405a 20]; Aristotle 1941b: 541). Anaxagoras (born c. 500 BC) names mind (nous) as the fundamental efficient cause of change. According to Aristotle, Anaxagoras ‘says that it was mind that set the whole in movement’ (On the Soul I, 2 [405a 19]; Aristotle 1941b: 541). Empedocles (ca. 494–434 BC) maintains that two forces, ‘love’ and ‘strife’, bring the four basic elements together and separate them.
Plato (428/427–348/347 BC) was the first to formulate what has become known as the principle of causality: ‘Everything which becomes must of necessity become owing to some cause; for without a cause it is impossible for anything to attain becoming’ (Plato, Timaeus 28a; as cited in Tabaczek 2019a: 4). Plato also introduces the notion of formal causality. Recognizing that material things are not knowable since they are always in flux, he sees them as mere shadows of an unchanging realm of forms or ideas that are truly real and knowable. Changeable things participate in such unchanging forms or exemplar causes.
Aristotle (384–322 BC) posits four intrinsically interrelated kinds of causes: material, formal, efficient, and final. He also answers Parmenides’ arguments against change. While agreeing that there is nothing in between being and non-being, he argues that there is nonetheless a principle between actual being and non-being. He calls this ‘possible’ or ‘potential’ being (being in potency). He criticizes Plato for inventing a separate world of forms and sees such talk as ‘empty words and poetical metaphors’ (Metaphysics I, ch. 9 [991a 8–22]; Aristotle 1941a: 707–708). Knowledge is grounded not in some separate world, but in the intelligibility or actuality of things in this world. Through the mind’s ability to abstract that intelligibility, we can have unchanging knowledge of the natures of changeable material things.
For Aristotle, forms are not extrinsic exemplars but intrinsic principles. Every changeable thing is composed of form and matter. The formal cause explains why a substance exists as a particular kind of thing, while the material cause accounts for why it can cease to be what it is and become something else. The efficient cause is the agent of change, like the sculptor who makes a statue. The final cause is the purpose or aim of a given action. It is that for the sake of which something is done, as a statue might be made the sake of beauty (Physics 2.3 [194b 23–35]; Aristotle 1941c: 240–241).
In the medieval period, Thomas Aquinas (1224/5–1274) AD) adopts and develops Aristotle’s philosophy (Rota 2011). He sees the hallmark of causality as ontological dependency: ‘Those things are called causes upon which things depend for their existence or their coming to be’ (Commentary on Aristotle's Physics 1.1. no. 5; Aquinas 1963: 5). He accepts Aristotle's teaching on the four causes and argues in his On the Truth of the Catholic Faith (Summa Contra Gentiles [SCG]): ‘Every cause is either matter, or form, or agent, or end’ (SCG 3.10 no. 5; Aquinas 1956: 56 [vol. 3]). Unlike Aristotle, however, he also finds a place for Plato's exemplar causes (Boland 1996). He sees these not as subsistent forms, but ideas in the mind of God: ‘In the divine wisdom are the types of all things, which types we have called ideas – i.e. exemplar forms existing in the divine mind’ (Summa Theologiae [ST] 1.44.3. co.; Aquinas 1946: 230 [vol. 1]).
For Aquinas, causality is an analogical notion that can be employed in a number of ways. The material stuff of the universe is a cause, but so are ideas in the mind of God. The artist is the cause of a statue, but so are its form or shape and the purpose for which it is made. A cause is always that upon which something depends for its being or becoming, but the modes of causality and dependency vary greatly depending on the kinds of causes involved. As Ignacio Silva points out: ‘This kind of causality as dependence opens the path to understanding causality as an analogical notion, where many different kinds of causality allow for several ways in which one thing can depend upon another for its being or change’ (Silva 2016: 161).
For both Aristotle and Aquinas, the four causes fundamentally explain two things: (1) why something is what it is and (2) why it can change and become something else. Matter and form are intrinsic causes that account for why something is what it is. Michelangelo’s Pietà, for instance, is made out of marble (material cause) and possesses a particular shape or form that causes that marble to be a statue (formal cause). If the marble lost that shape, it would no longer be that statue.
In addition to entering into the composition of a thing to explain what it is presently, the material cause also accounts for why it can cease to be what it is and become something else. Such change can occur on two levels: accidental and substantial. On the accidental level, a block of marble has the ‘potentiality’ to become a statue. The principle of potentiality or possibility is the material cause. In this example, it is a particular substance (marble). The marble is a thing which, while remaining that thing, is capable of accidental modifications in shape, size, and so forth.
On the substantial level, the principle of potentiality explains why a particular substance can cease to be that substance altogether and become something else. When a dog dies, for instance, it ceases to be one, organically unified substance and becomes a carcass – a collection of substances gradually breaking down into still more basic substances or elements. Although marble remains marble when a statue is broken, a dog does not remain a dog when it becomes a carcass. On the substantial level, the principle of possibility is not merely the potentiality of some substance to become differently shaped or structured, but the potentiality of one substance to become an entirely different kind of substance. Aristotle called this most basic principle of possibility ‘primary matter (prōtē hulē)’ (Physics, 2.1 [193a 29]; Aristotle 1941c: 237). It is the possibility, present in every material substance, to exist as a different substance (Luyten 1965). Again, on the substantial level, the formal cause is not merely an accidental form, such as size or shape. It is rather a substantial form, ‘that by which’ a thing is the sort of thing that it is (ST 1.110.2. co.; Aquinas 1946: 541 [vol. 1]). It is the principle that makes a thing to be the kind of thing it is and so accounts for the characteristic structure and activities it exhibits.
While Aristotle recognizes the actuality of substantial form and the potency of primary matter, Aquinas sees a deeper level of act and potency – the act of existing (esse) and the potency of essence. The substantial form makes the thing to be a particular kind of thing, but the act of existing (esse) causes the thing to exist rather than not exist (SCG 2.54; Aquinas 1956: 156–158 [vol. 2]). The discovery that essence is related to existence (esse) as potency to act is an insight belonging properly to Aquinas and not found in Aristotle (Judy 1976: 210). Every creature possesses an act of existing (esse) by which it is. In material things, this results in a twofold composition of act and potency. There is both a union of substantial form and primary matter and a combination of essence (matter and form considered together as ‘what it is’) and esse (the act of existing) (SCG 2.54. no. 9; Aquinas 1956: 157–158 [vol. 2]). Form or essence is a principle of potency with respect to the act of existing, which is ‘compared even to the form itself as act’ (SCG 2.54. no. 5; Aquinas 1956: 157 [vol. 2]). Esse is the act by which a thing exists. For this reason, as Aquinas explains in his On the Power of God, it is ‘the act of all acts and the perfection of all perfections’ (On the Power of God 7.2. ad 9; Aquinas 1952: 12 [vol. 3]).
To complete the account of how one thing can become something else, we must consider efficient and final causality. The efficient cause is the agent. This is broadly conceived. Aristotle describes it in his Physics as ‘the primary source of the change or coming to rest: e.g., the man who gave advice is a cause, the father is cause of the child, and generally what makes of what is made and what causes change of what is changed’ (Physics 2.3 [194b 30]; Aristotle 1941c: 241).
An efficient cause does not act except in view of some end or purpose, the final cause. The final cause, as a good to be attained, is what moves the agent to act, as one might exercise for the sake of health (Physics 2.3 [194b 33]; Aristotle 1941c: 241). Present not only in intelligent agents but also in things lacking intelligence, it is the foundation of all causal activity. As Aquinas says in The Principles of Nature, it is ‘the cause of the causality of all the causes’ (The Principles of Nature ch. 4, no. 24; Aquinas 1965: 19).
The notion of dependency is present in all four types of causality but applied in various ways. Each thing depends on its material and formal causes for its being since these are intrinsic to its nature. If they were removed, it would cease to exist. Each thing likewise depends on efficient and final causes for any change that it undergoes. The block of marble, for instance, would not become a statue apart from an artist with a particular goal in mind.
The notion of ‘action’ can be ascribed not only to the efficient cause, but also to formal and final causes: ‘A thing is said to act (agere) in a threefold sense. In one way formally, as when we say that whiteness makes white. [...] In another sense a thing is said to act effectively, as when a painter makes a wall white. Thirdly, it is said in the sense of the final cause, as the end is said to effect by moving the efficient cause’ (ST 1.48.1. ad 4; Aquinas 1946: 249 [vol. 1]). In Aquinas’ understanding, to act means ‘to make something to be in act’ (ST 1.115.1. co.; Aquinas 1946: 560 [vol. 1]). This can happen in a number of ways. If an artist shapes clay into a ball, for instance, we can say that they (the efficient cause) make the clay round. But we can also say that the form of ‘roundness’ makes the clay actually round. For all their pushing and pulling, the clay will remain only potentially round until it possesses that form or shape. We can also say that the final cause or end ‘acts’ on the agent or ‘moves’ the agent to act. If the artist works in order to make money, for instance, money (as a good to be attained) somehow induces them to act.
Efficient causality may sometimes, but not always, be described in terms of quantitative force. The activity of an artist, for instance, may be specified in terms of how many pounds of pressure per square inch they applie to the clay. The activity of the teacher who advises them, however, is also a type of efficient causality but cannot be described in terms of quantitative force.
Some kinds of causality can never be described as quantitative force. The formal cause, for instance, acts on the clay to make it actually round, but it does not act as a measurable force. It acts according to the mode of formal causality by causing something (in this case the spherical shape of the clay) to be actual. Its action is different from that of efficient causality, especially from the type of efficient causality known as ‘force’.
Likewise, final causality cannot be described quantitatively. The final cause induces the agent to act. If the artist works in order to make money, making money is in some way the cause of her action. But we cannot describe this influence in terms of quantitative force. The final cause acts, but it acts according to the mode of final causality, as an end or good that induces the efficient cause to act. The mode of causality proper to the final cause cannot be reduced to efficient causality, much less to the mode of efficient causality we call ‘force’.
In addition to these four causes, Aristotle and Aquinas also find a place for the causality of chance. As Aquinas explains: ‘From the concurrence of two or more causes it is possible for some chance event to occur, and thus an unintended end comes about due to this causal concurrence’ (SCG 3.74. no. 4; Aquinas 1956: 247 [vol. 3]). Since chance arises from a coincidence of causes, it is not seen as a direct (per se) cause, but an incidental (per accidens) cause. As Aristotle notes in his Physics: ‘Things do, in a way, occur by chance, for they occur incidentally and chance is an incidental cause. But strictly it is not the cause – without qualification – of anything’ (Physics 2.5 [197a 12–14]; Aristotle 1941c: 245).
For Aristotle and Aquinas, chance is a real feature of the natural world. As Aristotle says: ‘it is plain that there is such a thing as chance’ (Physics 2.5 [196b 14]; Aristotle 1941c: 244). Aquinas thinks that ‘it would be contrary to the character of divine providence if nothing were to be fortuitous and a matter of chance in things’ (SCG 3.74. no. 2; Aquinas 1956: 247 [vol .3]). The world teems with chance events. Aristotle says that chance is found not only in human affairs but also ‘in the lower animals and in many inanimate objects’ (Physics 2.6 [197b 14–15]; Aristotle 1941c: 246). Aquinas discovers it in all earthly things: ‘These things are said to be under the sun which are generated and corrupted according to the sun’s movement. In all such things we find chance: not that everything is casual which occurs in such things; but that in each one there is an element of chance’ (ST 1.103.5. ad 1; Aquinas 1946: 508 [vol. 1]).
2 Modern/contemporary thought
2.1 Modern science
Empirical science has exercised an enormous influence on the way we see the world. As Taede Smedes notes: ‘[W]ith the Enlightenment reception of science, something radically changed in the Western worldview. It eventually led to a situation in which the theories and methods of science came to shape and guide our thinking and attitudes. Since then, science no longer pertains solely to the material world, but also to the way we think about certain things; it guides our attitude towards reality in general’ (Smedes 2004: 208). Frederick Copleston observes: ‘It is simply an undeniable historical fact that philosophic reflection has been influenced by science both in regard to subject-matter and also in regard to method and aims. In so far as philosophy involves reflection on the world philosophic thought will obviously be influenced in some way by the picture of the world that is painted by science and by the concrete achievements of science’ (Copleston 1985: 275–276 [vol. 3]).
Among other things, science has profoundly influenced our understanding of causality. As Menno Hulswit explains:
The rise of modern science in the seventeenth century involved a radical change in the development of the concept of cause. Explanations by formal causation and final causation being rejected, efficient causation alone was considered to provide rational explanations of the phenomena. Moreover, the concept of efficient causation itself had radically changed. Whereas in the Aristotelian and scholastic tradition (a) efficient causation was not restricted to locomotion, (b) did not involve determinism and, (c) efficient causes were conceived as the active initiators of a change, in the seventeenth century the idea took hold that (a) all causation refers exclusively to locomotion, (b) that causation entails determinism, and (c) that efficient causes are merely inactive nodes in the chain of events, rather than active originators of a change. These changes have had a lasting influence on the evolution of our conception of cause, and indeed our entire Western outlook. (Hulswit 2002: 15)
In general, we can say that the meaning and scope of causality was narrowed with the advent of modern science, but has broadened again in contemporary science.
One hallmark of science is its quantitative method as devised by Galileo (1564–1642) (Weisheipl 1985). Convinced that the world could be studied only quantitatively, Galileo wrote that without mathematics ‘one wanders about in a dark labyrinth’ (Galilei 1957: 238). In accord with its method, science deals with observable phenomena that are mathematically representable and develops hypotheses or predictions that can be empirically tested. It therefore found no place for causes that could not be quantified. Formal and final causes were abandoned as ‘beyond the reach of experiment’ (Bunge 1979: 32; O’Rourke 2004: 22).
Isaac Newton (1643–1727) noted the mathematical motive behind the abandonment of certain types of causality: ‘The moderns, rejecting substantial forms and occult qualities, have endeavored to subject the phenomena of nature to the laws of mathematics’ (Newton 1946: xvii). Francis Bacon rejected both substantial forms and final causes in science. On forms, he writes: ‘Matter rather than forms should be the object of our attention, its configurations and changes of configuration, and simple action, and law of action or motion; for forms are figments of the human mind, unless you will call those laws of action forms’ (Bacon 1858b: 58). Of final causes, he says: ‘[T]he inquisition of Final Causes is barren, and like a virgin consecrated to God produces nothing’ (Bacon 1858a: 365).
Though science retained the notion of matter, it was no longer the unmeasurable ‘pure potency’ of Aristotle. Instead, it was viewed as the most basic actuality, the fundamental ‘stuff’ of the universe – the atoms or ultimate particles of which all things are composed. Of Aristotle’s four causes, only efficient causality remained since it alone could be expressed mathematically, observed empirically, and controlled experimentally. As John Keck notes: ‘Modern physics, by reducing all of nature to the quantifiable and measurable, has effectively eliminated all but one of the four causes’ (Keck 2007: 530–531). Mario Bunge observes: ‘[O]f the four Aristotelian causes only the efficient cause was regarded as worthy of scientific research’ (Bunge 1979: 32).
Though retained, the notion of efficient causality was itself contracted. It was no longer a broad enough concept to include such things as counselors who advise their leaders (Physics II, 3 [193b 30]; Aristotle 1941c). It was understood strictly in terms of the force or energy that moves the atoms of the universe (Burtt 1954: 30, 98–99, 208–209).
As a methodological strategy, there can be no objection to this limiting of the notion of causality. A purely quantitative method cannot embrace such non-quantitative notions as primary matter, formal causality, and purpose. Favouring quantitative explanations, the method gravitated towards a philosophy of mechanism. As Kirk Wegter-McNelly notes: ‘Embracing both the determinism and the reductionism of Newtonian science, early modern scientists quickly distanced themselves from modes of explanations that involved purpose, or telos. Increasingly they sought explanations couched exclusively in terms of efficient (i.e. mechanical) causes’ (Wegter-McNelly 2006: 160).
We can see the shift toward mechanistic explanations of material things in the thought of René Descartes (1596–1650). As Frederick Copleston notes: ‘Descartes [...] considered that the material world and its changes can be explained simply in terms of matter, identified with geometrical extension, and motion. At creation God placed, as it were, a certain amount of motion or energy in the world, which is transmitted from body to body according to the laws of mechanics’ (Copleston 1985: 290 [vol. 3]). Descartes expresses this as a principle:
That God is the primary cause of motion; and that He always preserves the same quantity of it in the universe. [...] As far as the general (and first) cause is concerned, it seems obvious to me that this is none other than God himself, who (being all powerful) in the beginning created matter with both movement and rest; and now maintains in the sum total of matter, by His normal participation, the same quantity of motion and rest as He placed in it at that time (Descartes as quoted in Hulswit 2002: 18, original emphasis).
The primary cause is God, and the secondary causes are the laws of nature, a concept that Descartes himself invented (Koperski 2020: 6; Schmaltz 2014: 156–159). As Descartes explains: ‘Furthermore, from this same immutability of God, we can obtain knowledge of the rules or laws of nature, which are the secondary and particular causes of the diverse movements which we notice in individual bodies’ (Descartes as quoted in Hulswit 2002: 18). Menno Hulswit summarizes Descartes’ teaching on causation:
In the beginning, God created matter and motion, and he conserves exactly the same quantity of motion for all time. There can be no locomotion – change of place – unless there be some kind of force or power. Since such force was not inherent in matter – ‘extension’ in no respect involves ‘force’ – God is the efficient cause of any change of motion in an otherwise inert matter. And He does so according to the laws of nature, which became secondary causes. Thus, Descartes attributed some efficient causality to the laws of motion, which determine all particular effects. By doing so they provide causal, mechanical explanations. On the other hand, Descartes maintains that the only ‘active initiator of change’ is God, the cause of all causes. (Hulswit 2002: 18)
Influenced by the mathematics and mechanism of modern science, Descartes found no place for the traditional notions of form and matter in his account of the natural world (Wallace 1996: 18). Lacking the explanatory principle of substantial form as a spontaneous source of activity, Descartes names God as the sole source of motion. This inclines him towards occasionalism. As Kenneth Clatterbaugh says: ‘We are left with the conflict that on the one hand Descartes seems clearly to think that bodies act on other bodies and on the other he has no metaphysical story that tells how this could happen’ (Clatterbaugh 2012: 59).
Tad Schmaltz notes that ‘a central question [...] is whether Descartes allows for any causes other than God’. He acknowledges Descartes’ statement that God is ‘the universal and total cause’, but defends ‘a reading on which such a claim endorses not the occasionalist conclusion that God is the only cause of natural effects, but rather the more modest conclusion that all other causes of natural effects are subordinated to God’s universal causality’. For Descartes, as Schmaltz explains, God ‘is not a cause of change. Rather he is the cause of a constant quantity of motive force in the world’ (Schmaltz 2008: 76, 90, 104, 218).
The upshot for causality was that formal, final, and material causality (as pure potentiality) were not simply omitted methodologically but denied ontological existence. As James Weisheipl explains: ‘The essential feature of this mechanical philosophy was the rejection of physis, or nature, as an explanatory principle in natural science. With this rejection also went potency and act, substance, formal and final causality, and even the ontological reality of true causality’ (Weisheipl 1985: 260).
The term ‘causality’ was no longer an analogical notion, applicable to a range of causes, but a univocal idea applied to the only type of causality to be found in the cosmos – the efficient causality of the energy that moves the atoms. As Fran O’Rourke explains: ‘Causality is viewed as an external, efficient relation; Aristotle’s comprehensive understanding of aitia is abandoned. Reduced in this manner to the dimensions of external extension, the natural world is [...] deprived of its inner dynamism and natural tendency’ (O’Rourke 2004: 23–24).
With David Hume (1711–1776), even this narrowed idea of efficient causality was questioned. Since the supposed influence of a cause upon its effect was not directly evident to sense observation, Hume concluded that the connection between cause and effect was not an aspect of the real world, but only a habit of our thinking as we become accustomed to see one thing constantly conjoined to another (Hume 2000: 49–61; Kail 2014). Hume sees causes not as things (as in Aristotle) but as events. As Rom Harré explains:
Instead of causality as a process in which active agents exercise their causal powers, the regularity analysis is based on the presumption that causes are events. [...] According to Hume [...] the causal relation as it is thought to hold between a pair of events, one the cause and the subsequent event the effect, includes three components. There must be regular concomitance in contiguity and succession between the types of events of which the cause event and the effect event are instances. [...] As well as regular contiguity and succession the idea of causality includes the idea of necessity, that is the idea that the effect event must follow the cause event, ceteris paribus. (Harré 2005–2006)
In this way, Hume originated the notion of ‘event causation’ which has taken many forms in contemporary philosophy and science (Hulswit 2004: 3–5).
For Immanuel Kant (1724–1804), causality is also an aspect of thought, not acquired through cumulative experience as in Hume, but known a priori. As Frederick Copleston explains: ‘If I say that every event must have a cause, my judgment expresses a priori knowledge: it is not simply the expression of an habitual expectation mechanically produced by the association of ideas. The necessity, Kant insists, is not “purely subjective”; the dependence of any event or happening or change on a cause is known, and it is known a priori’ (Copleston 1985: 218 [vol. 6]).
Causality became a property not of things but of thought. It was no longer an ontological reality in the world outside ourselves, but an epistemological property of the way we think about the world. The hallmark of causality was now found in the epistemological category of predictability rather than the ontological category of dependence. As Mario Bunge notes: ‘Unlike causation, which is an ontological category, predictability is an epistemological category’ (Bunge 1979: 327).
The very success that science enjoyed by omitting causes that could not be measured eventually led to the conviction that such causes may be not only ignored methodologically but denied metaphysically. The methodological assumptions that science had used for studying the world became ontological assertions about its nature. Add to this the conviction that all of reality is quantitative and that empirical science alone is capable of investigating it, and one transforms the valid and successful methodology of science into the ideology of scientism (Haak 2003; Słomka 2021: 142–144; Wiertz 2016: 49–51).
2.2 Contemporary science
With the discoveries of contemporary science, new ways of understanding causality have arisen. We can see this in the theories of quantum mechanics, emergence, Big Bang cosmology, and contemporary biology. Quantum theory (at least in the Copenhagen interpretation) has affirmed a world of spontaneity with a fundamental indeterminism as the foundation of material reality (Polkinghorne 2006: 979). Such indeterminacy brings to mind Aristotle’s material cause – not the actual, measurable ‘stuff’ of Newtonian science, but a principle of mere possibility (primary matter) inherent in every substance. Werner Heisenberg himself was aware of this association (Heisenberg 1958: 160).
The theory of emergence claims that, at many levels in the natural world, new features arise with distinctive causal influences that cannot be explained simply by reference to their parts (Clayton 2006: 66–69; Tabaczek 2013). To study them, one must begin with the whole (from the top down) rather than the part (from the bottom up). George Ellis points out that ‘top-down action affects the nature of causality significantly’ and can ‘modify the properties of the constitutive elements at the lower levels’ (Ellis 2006: 753) The ‘bottom-up’ method of reductionism no longer seems adequate for explaining the phenomena that science observes. The move away from reductionism to the ‘top down’ causality of the whole invites a reconsideration of Aristotle’s notion of substantial form as an intrinsic principle that makes the whole substance to be what it is (Tabaczek 2019a).
Big Bang cosmology involves a notion of potentiality reminiscent of Aristotle’s material causality. As biologist Christian de Duve observes: ‘The universe has given life and mind. Consequently, it must have had them, potentially, ever since the Big Bang’ (de Duve 2002: 298). The initial formation of the universe involved myriad contingencies. If any one of these had been slightly different, a universe capable of producing and sustaining human life might never have developed. To explain such intricacies, some scientists have suggested an ‘anthropic principle’. This introduces human beings into the equations (Bartholomew 2008: 82–85; Barrow and Tipler 1986; Rolnick 2015: 129–146). Somehow the ‘wherefrom’ of the universe in the interrelation of initial forces is intricately related to its ‘whereto’ in the eventual emergence of rational life. The notion of nature’s ‘whereto’ invites a reconsideration of purpose (Aristotle’s final cause) as a category of explanation in the natural world. Contemporary biology has also embraced the notion of purpose or final causality. As Francisco Ayala argues: ‘[T]eleological explanations in biology are not only acceptable but indeed indispensable’ (Ayala 1998: 44).
Potentiality, form, and finality are all modes of causality that are not measurable and so cannot come directly under the scientific microscope. What is studied and discovered in science, however, now seems to invite their consideration as categories of explanation (Wallace 1996; for more on this topic see The History of Science and Theology).
3 Causality and divine action
We can now consider the implications of these changes in the general concept of causality for the discussion of divine causality. We begin with a theological reflection on causality in scripture.
3.1 Causality in scripture
The language of causality is to be found on practically every page of scripture. Throughout the Bible, we find God and human beings (as well as animals and elements) doing things and causing things. In the poetic opening verses of Genesis, God creates the heavens and the earth. Light comes into being at his command, ‘let there be light’ (Gen 1:3). God acts directly in the formation of the firmament, the seas, and the dry land. God then works indirectly through the things he has made, initiating a veritable cascade of causal events (Chambers 2019: 12). He commands the earth to put forth vegetation, and it produces plants bearing their seed (Gen 1:11–12). He wills that the waters and the earth bring to forth living creatures, resulting in sea creatures, cattle, and creeping things (Gen 1:20–25). Finally, God makes human beings: ‘Let us make humankind in our image, according to our likeness’ (Gen 1:26). He allows humans share in his causality, giving them dominion over all other creatures (Gen 1:28–30).
Such causal themes continue throughout scripture. We find them in the poetry of the psalms: ‘You make springs gush forth in the valleys; they flow between the hills, giving drink to every wild animal’ (Ps 104:10–11). Patriarchs and prophets are presented as instruments in achieving God’s salvific plan. In all of these stories, God is the fundamental cause: ‘O Lord, you will ordain peace for us, for indeed, all that we have done, you have done for us’ (Isa 26:12). As Joan Cook explains: ‘In ancient Israel the biblical authors had the task of ascribing all divine interventions to the one God. [...] Within this worldview the Hebrew Bible frequently reports that the Deity commissioned humans to carry forward the divine work of governing and protecting the people’ (Cook 1999: 20). Sometimes, however, humans seem to be the initiators. Again, as Cook notes, ‘On the other hand, the divine purpose was influenced and even changed by human initiative. For instance, Abraham pleaded with God to spare the city of Sodom (Genesis 18:32)’ (Cook 1999: 21).
In the New Testament, Jesus is the fundamental instrument of the Father’s salvific will (John 3:16), and his followers somehow share in his mission. We might say that God, as primary cause, acts through them as secondary causes. So, St. Paul states: ‘Now there are varieties of gifts, but the same Spirit; and there are varieties of services, but the same Lord; and there are varieties of activities, but it is the same God who activates all of them in everyone’ (1 Cor 12:4–6). And again: ‘Such is the confidence that we have through Christ towards God. Not that we are competent of ourselves to claim anything as coming from us; our competence is from God, who has made us competent to be ministers of a new covenant’ (2 Cor 3:4–6).
It is the task of theology as ‘faith seeking understanding’ to ponder such scriptural language. This work requires the integration of many academic disciplines (Bartholomew 2020). It relates the biblical account of the act of creation (Gen 1:1–2:25; 2 Macc 7:28) to the theological tradition of creation from nothing (creatio ex nihilo) (Pelikan 1960; Ticciati 2017; Carroll 2011: 10–13; Abraham 2018: 127–141). It also engages the question of how divine causality may be related to that of creatures. (Amit 1987; Grossman 2007; Gericke 2015; Chambers 2019). This includes the discussion of scriptural passages in which human actions seem to provoke a divine reaction (Jas 4:8) including grief, sorrow, and repentance: ‘And the Lord was sorry that he had made humankind on the earth, and it grieved him to his heart’ (Gen 6:6; 2 Sam 24:16; Jer 18:8–9). Some theologians see such passages as assertions that God is affected by the actions of creatures (Pinnock et al. 1994). Others interpret them in ways that preserve the traditional divine attributes of immutability and impassibility (Dodds 2008; Dolezal 2017).
Theology also considers how our philosophical presuppositions may influence our interpretation of scripture. A philosophy of naturalism that denies all supernatural causality must interpret all statements about divine agency as metaphors. Mere conservationism allows that God acts, but only in the initial creation and subsequent preservation of the world. Occasionalism attributes all causality to God, denying the causality of creatures. Concurrentism allows for the affirmation of both divine and creaturely causality (Freddoso 1994: 133–134).
3.2 Divine action and the narrowed notion of causality in modern science
We have already seen how the notion of causality was contracted with the advent of modern science and expanded by the discoveries of contemporary science. We can now examine the consequences of this for the discussion of divine action.
The contracted notion of causality limits our ability to speak of God’s action. In a classic article, Langdon Gilkey asserts: ‘Contemporary theology does not expect, nor does it speak of, wondrous divine events on the surface of natural and historical life. The causal nexus in space and time which Enlightenment science and philosophy introduced into the Western mind [...] is also assumed by modern theologians and scholars’ (Gilkey 1983: 31).
If causality itself consists only of physical force, then divine causality must be thought of as one physical force among others. But when God’s action is conceived in this way, it inevitably appears to interfere with other forces and with the laws of nature that describe them. If there is but one univocal sort of causality, God must also employ it and so become just one more cause among others. When two univocal causes are involved in the same action, however, the causality of one inevitably interferes with that of the other. If two people carry a table, for instance, each lifts only part of the total load. The result is a zero-sum game. The more weight one bears, the less there is for the other. Similarly, if we think of God as a univocal cause, God’s causality must interfere with that of creatures. An omnipotent God would then necessarily rob all creatures of their proper causality. Faced with this dilemma, some theologians concluded that God’s power must be limited.
Such divine limitation takes various forms. Deism limits God’s action to the moment of creation. God made the world but is no longer needed to explain its continued existence and activity. Some liberal theologians allow that God continues to act in the world, but find his action limited by the laws of nature. Friedrich Schleiermacher argues, for instance, that ‘as regards the miraculous, the general interests of science, more particularly of natural science, and the interests of religion seem to meet at the same point, i.e. that we should abandon the idea of the absolutely supernatural’ (Schleiermacher 1960: 183). Rudolf Bultmann considers it inappropriate to view divine action as a cause ‘which intervenes between the natural, or historical, or psychological course of events’. Events in nature are ‘so linked by cause and effect’ as to leave ‘no room for God's working’ (Bultmann 1983: 61, 64). As Craig Bartholomew explains: ‘A common tendency in modernity has been to see its naturalistic, scientistic worldview as true and superior to theistic worldviews, with the divine element in the latter as mythical, and in need of demythologization’ (Bartholomew 2020: 178, original emphasis).
To avoid divine interference, some theologians limit God’s knowledge and power. Arthur Peacocke argues that ‘God’s omniscience and omnipotence must be regarded, in some respects, as “self-limited”’ (Peacocke 1993: 155). John Polkinghorne thinks that the presence of chance in the world requires a limitation of divine power: ‘God chose a world in which chance has a role to play, thereby [...] accepting limitation of his power to control’ (Polkinghorne 1989a: 63; Schaab 2008: 14–17). Theologians tend to limit God’s action when it appears to disturb or interfere with the causality of creatures and the nexus of scientific laws. But God’s action must involve such a disturbance so long as it is understood as a univocal cause. There will be no other way to understand it, however, if causality itself is reduced to a univocal notion.
3.3 Divine action and the expanding notion of causality in contemporary science
The discoveries of contemporary science suggest two fundamentally new options for speaking about God’s action. One is to use the new discoveries of science themselves in theology. The other is to employ the expanded notion of causality that they imply.
3.3.1 Employing the new discoveries of science to speak of divine action
A prime example of employing the discoveries of science theologically is the monumental work of the ‘Divine Action Project’, a cooperative effort of theologians, scientists, and philosophers sponsored by the Vatican Observatory and the Center for Theology and the Natural Sciences at the Graduate Theological Union in Berkeley, California. Their work flowered in many distinguished publications (Russell, Murphy, and Stoeger 2008) and continues to draw critical comment (Smedes 2008; Henry and Tabaczek 2017: 386–391; Fergusson 2018: 217–225; Willliam J. Abraham 2017: 146–164; Jung 2012; Plantinga 2011: 97–121; Słomka 2021).
The indeterminism of quantum mechanics has been used extensively in the discussion of divine action (Barbour 2002: 104–105). Robert Russell maintains that ‘we can view God as acting in particular quantum events to produce, indirectly, a specific event at the macroscopic level, one which we call an event of special providence. [...] Quantum mechanics allows us to think of special divine action without God overriding or intervening in the structures of nature’ (Russell 1998: 89, 94; Russell 2018). Thomas Tracy presents similar arguments (Tracy 2015: 139; Tracy 2006: 601; Tracy 2013: 460–463).
John Polkinghorne employs the openness and top-down causality of chaos theory as an arena that leaves ‘room for divine maneuver’ (Polkinghorne 1989b: 31; Polkinghorne 2006: 979; Polkinghorne 2011: 39–40, 85–88; Karaba 2021). Arthur Peacocke uses the theory of emergence to suggest how God may act through top-down causality on the world as whole ‘without abrogating any of the laws (regularities) which apply to the levels of the world’s constituents’ (Peacocke 2006: 274–275; Tabaczek 2021: 137–140, 182–185). Other theologians have utilized the anthropic principle to affirm that divine design is involved in the ‘fine tuning’ of the early universe to ensure that it would be a place suitable for human life (Bartholomew 1984: 31–32, 64; Spitzer 2010: 47–74; Meyer 2021: 130–164; Plantinga 2011: 193–224).
Putting the discoveries of science to theological use in these ways has been enormously helpful in the dialogue between theology and science. Still, it raises certain problems. First, when a theology is tied to a specific interpretation of a particular theory of science, it can remain viable only as long as that theory is considered valid (Fergusson 2018: 222–224). A second problem arises when God’s action is invoked to explain some natural phenomenon (such as the fine tuning of the early universe) for which there is as yet no scientific explanation. Since science has a way of filling in such gaps in its account of the natural world, the god who acts in them has become known as the ‘god of the gaps’, a god who is constantly retreating before the advance of science. A third problem is entailed in a theology that locates God’s causality within scientific indeterminacies in order to avoid divine interference with the causality of creatures. Since only univocal causes can manifest such interference, such a theology seems to assume that God’s causality is the same as that of creatures and so imply that God is just one cause among others (Balsas 2017: 101). Such problems by no means invalidate this approach to divine action, but they do suggest that a certain caution is needed. An alternative approach would be to employ not so much the discoveries of science as the broader notion of causality that they imply.
3.3.2 Employing the new notion of causality to speak of divine action
Through its discoveries, science seems to be reaching towards a multifaceted account of causality. This would invite a retrieval of certain classical notions of causality such as material, formal, efficient, and final causes (Dodds 2012; Tabaczek 2021; Balsas 2017: 123–160; Watkins 2019: 23–24).
The first thing to note here is that there is a fundamental difference between divine and creaturely action. While the action of creatures is incidental to them, God’s action is one with his being. As Aquinas teaches: ‘God’s action is his being (Suum agere est suum esse)’ (SCG 2.9. nos 4–5; Aquinas 1956: 40–41 [vol. 2]). We must not think of divine and creaturely action as univocal, but neither should we consider them equivocal. Because God is the cause of creatures and because every effect is in some way like its cause, creatures are in some way like God (ST 1.4.3. ad 4; Aquinas 1946: 23 [vol. 1]). We can therefore speak of divine action analogously (as we speak of other divine attributes), using words that are normally applied to creatures (ST 1.12.12; 1.13.5; Aquinas 1946: 58–59, 63–64 [vol. 1]; Rocca 2004; McInerny 1996).
A rich vocabulary and conceptual framework for speaking of divine action analogously is available in the classical notions of formal, efficient, and final causality. God is the final cause of each creature. Since every action of the creature is for the sake of some real or apparent good, and each thing is good only insofar as it participates in a likeness to the Supreme Good, who is God, ‘it follows that God himself is the cause of every operation as its end’ (ST 1.105.5; Aquinas 1946: 518 [vol. 1]). As final cause, God is intimately involved in every action of creatures. God does not interfere with such action, but is rather its source.
God is the exemplar formal cause of all things. As the idea or exemplar in the mind of an artist is the source of her art, so God is the cause of all creatures as ‘the first exemplar cause of all things’ (ST 1.44.3. co.; Aquinas 1946: 231 [vol. 1]). As the creative idea of the artist does not interfere with her art, but is rather its origin, so God, acting as exemplar cause, does not interfere with causality of creatures.
God is also the first efficient cause. This is manifest most profoundly in his work as creator, giving being to all things (ST 1.3.4. co., 1.44.1. co.; Aquinas 1946: 17, 229). Since being is the innermost actuality of each creature, God is most intimately present to each creature. As Aquinas says: ‘Being is innermost in each thing and most fundamentally inherent. [...] Hence, it must be that God is in all things and innermostly’ (ST 1.8. co.; Aquinas 1946: 34 [vol. 1]).
God’s efficient causality is also manifest in acting as primary cause through the secondary causality of creatures. Insofar as the effect of such action entails being and perfection, it is fully from God and fully from the creature. As Aquinas says: ‘It is apparent that the same effect is not attributed to a natural cause and to divine power in such a way that it is partly done by God and partly by the natural agent; rather, it is wholly done by both, but in different ways’ (SCG 3.70. no. 8; Aquinas 1956: 237 [vol. 3]). In this way, God acts through creatures without imposing necessity on them or depriving them of their own proper causality:
[T]he divine will must be understood as existing outside of the order of beings, as a cause producing the whole of being and all its differences. Now the possible and the necessary are differences of being, and therefore necessity and contingency in things and the distinction of each according to the nature of their proximate causes originate from the divine will itself, for he disposes necessary causes for the effects that he wills to be necessary, and he ordains causes acting contingently (i.e. able to fail) for the effects that he wills to be contingent. And according to the condition of these causes, effects are called either necessary or contingent, although all depend on the divine will as on a first cause, which transcends the order of necessity and contingency. (Commentary on Aristotle's On Interpretation 1.14. no. 22; Aquinas 1962: 118–119; ST 1.22.4; Aquinas 1946: 124 [vol. 1]; Dodds 2012: 205–210)
Chance events also retain their contingent character when God acts through them. As Lydia Jaeger observes: ‘[I]t is possible to believe in God’s sovereignty over everything and to accept that certain events count as chance on the scientific level. A clear distinction between the primary transcendent cause and secondary natural causes leads us to understand that something can be part of God’s plan, without having a natural cause. Those who believe in divine omniscience and omnipotence should not be bothered by chance and its important role in contemporary science’ (Jaeger 2015: 161). This is especially helpful in understanding God’s action in biological evolution (Tabaczek 2019b; O’Rourke 2004).
4 Divine action and the believing community
Prayer is intimately related to the question of divine action. As Nicholas Saunders notes: ‘It is of primary importance [...] for Jewish and Christian theology to encompass divine action; if God is unable to act, then even petitionary prayer is useless: there is simply no way for God to “give us our daily bread”’ (Saunders 2000: 518). With the advent of contemporary science, theologians have found new ways to speak God’s action with respect to prayer. Some use the scientific discovery of indeterminism; others employ the expanded notion of causality that science now implies.
Keith Ward illustrates the first approach, where ‘divine action will be a causal influence that works within the parameters of probabilistic physical law. God might console me when I am in trouble, or might heal someone in answer to my prayer. This can happen without breaking any laws of nature’ (Ward 1998: 89). There are, however, certain liabilities to this approach arising from the very physics of quantum indeterminacy as Timothy Sansbury has noted (Sansbury 2007: 117).
The second approach sees God’s primary causality as the ultimate source of all our actions including prayer. The fundamental dynamic of prayer is not that we pray first and then God responds, but rather that God prays in us: ‘In the same way, the Spirit too comes to the aid of our weakness; for we do not know how to pray as we ought, but the Spirit itself intercedes with inexpressible groanings’ (Rom 8:26). As C. S. Lewis observes: ‘The deeper the level within ourselves from which our prayer, or any other act, wells up, the more it is His, but not at all the less ours. Rather, most ours when most His’ (Lewis 1964: 69).
We can see prayer as a secondary cause under the influence of God’s primary causality. As God acts through secondary causes such as food and air in preserving our natural life, so God may act through prayer in fostering our spiritual life. As our physical life would be jeopardized if we did not make use of the secondary causality of food, so our spiritual life may suffer if we fail to employ the secondary causality of prayer (SCG 3.96. no. 8; Aquinas 1956: 62 [vol. 3]).
Seeing prayer as a secondary cause reminds us that the purpose of prayer is not to change God but to change us. As secondary causes in nature do not change the divine causality that works through them but are rather moved by it, so prayer is not meant to change God, but to transform us. As Aquinas says, ‘[p]rayer is not established for the purpose of changing the eternal disposition of providence’ (SCG 3.95. no. 1; Aquinas 1956: 58 [vol. 3]). Prayer does not awaken God’s love for us (which is ever present), but it may quicken our love for God. Through prayer, we come to see God more clearly, surrender more completely, and so become more transformed into God’s likeness.
The question of miracles has been a particular focus in the theology/science dialogue (Göcke 2016). David Hume defined a miracle as a ‘violation of the laws of nature’ and argued that the very notion of miracle is incoherent (Hume 2000: 86–87). Accepting Hume’s definition, some thinkers have considered science incompatible with miracles (Wiles 1994: 26). Rudolph Bultmann famously argued: ‘It is impossible to use electric light and the wireless and to avail ourselves of modern medical and surgical discoveries, and at the same time to believe in the New Testament world of spirits and miracles’ (Bultmann 1961: 5). Hume’s definition of miracle as a ‘violation of the laws of nature’ implies a conflict between theology and science. Lydia Jaeger defuses the potential conflict by explaining the character of the laws of nature:
Any law only applies if all acting causes are taken into account. That is the reason why it is not correct to define a miracle as a violation of the laws of nature. It is instead the intervention of an external cause, and more precisely of a non-natural cause. Laws of nature describe what normally happens, under the condition that such an external action (apart from general providence) is absent. The ordinary formulation of laws leaves this condition implicit, which leads to the wrong impression that such an intervention would violate them. (Jaeger 2015: 156–157)
Scientist/theologian Robert Russell sees no conflict between science and miracles. As he avers: ‘I fully believe God can also act in truly miraculous ways’ (Russell 2018: 141). Thomas Tracy maintains: ‘If God is the free creator of the entire system of natural law, then God surely could choose to act in the world in ways that exceed the causal powers of creatures’ (Tracy 2006: 600).
To defuse the potential conflict between miracles and science, Aquinas’s definition of miracle may be preferable to Hume’s. He sees a miracles fundamentally not as violations of nature, but as simply beyond nature:
The word ‘miracle’ is derived from admiration, which arises when an effect is manifest, whereas its cause is hidden. [...] Now a miracle is so called as being full of wonder, as having a cause absolutely hidden from all; and this cause is God. Wherefore those things which God does outside [praeter] those causes which we know are called miracles (ST 1.105.7. co.; Aquinas 1946: 520 [vol. 1]).
In On the Power of God, Aquinas poses the question, ‘Can God do anything in creatures that is beyond (praeter) natural causes, or against (contra) nature, or contrary to (contra) the course of nature?’ (On the Power of God 6.1; Aquinas 1952: 150). His basic answer is ‘yes’, but it is nuanced by considerations of the various relationships of nature in his cosmology. The most basic relationship is that of all creatures to God. In this sense ‘God does nothing contrary to (contra) nature’ (On the Power of God 6.1, ad 1; Aquinas 1952). There are also natural relationships among creatures and, with respect to them, God may be said to act ‘against (contra) nature’ (On the Power of God 6.1, ad 1; Aquinas 1952). Elsewhere, Aquinas offers further nuances:
If we consider the order of things depending on the first cause, God cannot do anything against (contra) this order; for if he did so, he would act against his foreknowledge, or his will or his goodness. But if we consider the order of things depending on any secondary cause, thus God can do something outside (praeter) such order; for he is not subject to the order of secondary causes, but on the contrary this order is subject to him as proceeding from him not by a natural necessity, but by the choice of his own will; for he could have created another order of things. Wherefore God can do something outside (praeter) this order when he chooses, for instance by producing the effects of secondary causes without them or by producing certain effects to which secondary causes do not extend. (ST 1.105.6. co.; Aquinas 1946: 519 [vol. 1])
Since God is the creator, the universe is ordered to his goodness as its ultimate end or final cause. Each thing is directed by its nature towards a particular end that is a reflection and participation of the transcendent goodness of God. Human beings are directed in a special way towards that end, since God wills them to share in his own life. It is therefore appropriate for God to act miraculously in the world to direct humans to this end as Aquinas explains in On the Power of God:
When God does anything contrary to the course of nature, the whole order of the universe is not subverted, but the course resulting from the relation between one particular thing and another. Hence it is not unfitting if at times something is done contrary to the course of nature for man’s spiritual welfare which consists in his being ordered to the last end of the universe. (On the Power of God 6.1, ad 21; Aquinas 1952: 161 [vol. 2])