4.1 Doctrinal background to medieval theories of divine simplicity
Medieval Christian theological reflections on divine simplicity are manifold, and in fact extremely diverse. The treatment of the topic by various well-known theologians is far from homogeneous. On the contrary, it is often indicative of ideas proper to a given thinker. However, parameters of unity were provided by several factors. One of these was the thought of Augustine on divine simplicity, which acted as a proximate inspiration for most Western theologians. Likewise, there were two important public debates in the twelfth century regarding trinitarian theology that led to ecclesiastical formulations of a doctrine of divine simplicity. The first of these had to do with the claims of Gilbert of Poitiers (d. 1154), which were rejected by the Council of Reims in 1148. Gilbert noted that the essence of the three persons in God must be one and the same, since they are each the one God. He concluded from this, however, that the relations of origin between the persons must be something distinct from their essence, since the essence unites them, but the relations distinguish them. He concluded that there must be a distinction between each of the persons and their relative properties, since each person is essentially God and is related to others only accidentally (Expositio in Boecii de Trinitate 1.5, nos. 42–42; in Gilbert of Poitiers 1966: 148; Emery 2007: 90–91). According to this view, relations are accidental to the substance of a trinitarian person, much as they would be in human persons. God the Father is not identical with his paternity or his relation to his Son. Rather, he merely possesses paternity, while sharing the essence of God with the Son. In this way of thinking, the three persons of the Trinity are conceived of as relatively similar to three human beings identical in essence (as human), and related merely by accidents or properties (as in a father and son relation, for example). This position was criticized by Bernard of Clairvaux and condemned by the Council of Reims because it failed to acknowledge the simplicity of the divine nature of the Trinity, along the lines indicated by Augustine (Evans 2000: 75–77, 123–127). On Augustine’s view the relations of the persons are not accidental additions to a substance, but pertain in some mysterious way to the very substance of the divine persons.
This Augustinian medieval idea of the Trinity is apophatic in many respects, since it implies that the divine communion of persons in God is utterly dissimilar to the relations of human persons. However, it does also suggest that we can think of the persons in the Trinity by analogy with created persons, if we take divine simplicity (and thus divine transcendence) into account. Such an idea was developed more expressly at the Fourth Lateran Council in 1215 which took issue with the theology of Joachim of Fiore (d. 1202). Joachim had written against Peter Lombard who had affirmed in his writings that one may not say that the essence of God begets or spirates. By error, Joachim believed that this claim implied that Lombard was treating the essence in God as a kind of additional fourth subject, really distinct from the three persons who are subject to begetting and spiration. He responded by affirming that the essence of God begets and spirates, and in doing so, attributed processional activities to the essence of God. On this view the persons seem to each have distinct essential attributes that differentiate them, such as natural begetting or natural being begotten. Therefore, they seem to have essential differences (that is to say differences of essence), and so to be united as one only morally or ethically as in a communion of human persons, who are not truly consubstantial. Joachim may have wished to indicate that the eternal processions of the trinitarian persons just are what God is (the processional life of Father, Son, and Spirit). However, in the process, he affirmed that the essence itself differentiates in composite ways, due to the divine processions. The Fourth Lateran Council rejected this view by explicitly appealing to the simplicity of the divine nature (Tanner 1990: 232 [vol. 1]). The Trinity is more dissimilar than similar to a communion of created persons. The Father, Son, and Holy Spirit are distinguished only by relations of origin, but these are not properties or accidents. The whole substance of the godhead is communicated from the Father to the Son by eternal generation and from the Father and the Son to the Holy Spirit by eternal spiration. Each person thus possesses the fullness of the deity in its perfection and simplicity, and each person is truly the one God.
Theologians in the medieval Catholic Church saw rightly that both of the problematic positions noted above fail to understand sufficiently the implications of the doctrine of divine simplicity. If the nature of God is simple, then there cannot be personal relations in God that are extrinsic to his essence. Nor can God’s nature be subject to diverse composite activities of self-differentiation, like begetting and spirating. The three persons are distinct, but they are only truly one in essence because each person of the Holy Trinity partakes fully of the one divine nature of God.
4.2 Thomas Aquinas on divine simplicity
Aquinas treats the doctrine of divine simplicity in multiple places in his corpus, but this article concentrates on his mature positions presented in the Summa Theologiae (ST), especially ST: q. 3 (part I), as well as in the treatment of trinitarian relations and persons in qq. 28–29, which, it shall be argued, is a logically related topic. In ST: q. 3 (part I), Aquinas discusses various forms of ontological composition that pertain to creatures, or logical complexity that pertains to our way of thinking conceptually about creatures, and he systematically denies that such forms of composition pertain to the divine nature. He thus denies that our logical conceptions of composition can be rightly ascribed in a literal way to God. It is important to note that in this context (ST: q. 3 [part I]) Aquinas is reflecting on the mystery of the divine essence, which Christian theology claims is proper to all three trinitarian persons (homoousios). Therefore, his reflections on divine simplicity are organically related to a broader vision of trinitarian theology that is being explored. Here four of the principal forms of composition in creatures and non-composition in God that Aquinas treats will be noted, all of which have some foundation in the biblical and patristic material noted above, and all of which have consequences for Aquinas’ understanding of the Trinity.
4.2.1 Form and matter
Following Aristotle, Aquinas thinks that every physical, material being that humans experience in the cosmos is a form-matter composite (Aquinas, Opusculum De Principiis Naturae: cc. 3–8 [see 1954]). ‘Form’ in this context designates the substantial determination of a given thing such that it has a nature of a given kind and properties that are specific to that nature. The form of an orange tree, for example, is its genus and species. Each tree falls within the genus of vegetative living things, and additionally within the species of trees that produce a distinctive kind of fruit, according to its organic constitution and material properties. Understood in this way, the form of a physical reality accounts for its nature, properties, and sameness of kind, relative to others. Matter, meanwhile, denotes the physical component parts of a natural form, as well as the radical potency present in and through all the material parts, such that every physical reality is potentially subject to indefinite transformation, by substantial corruption and the subsequent generation of new forms. Even though it is always subject to potential transformation, the matter of any given reality is also always actuated by the natural form such that all the material parts are organized and arranged as parts of a given kind of thing, and they express the nature and properties of that form, in and through their material configurations. The material body of a hound is different from the material body of a human being, a fir tree, or a lake.
In virtue of these two principles, which are always present and mutually implicated in all material bodies, every physical reality we come to know is ontologically composite. Why then would we not ascribe a similar kind of ontological composition to God? Aquinas gives several reasons (ST: q. 3, a. 2 [part I]). One is that any material thing is inevitably subject to passive change due to the action upon it by other realities, and therefore is a reality caused by and ontologically dependent upon other realities. However, God the Creator is, by biblical definition, the one who gives being to all created realities. It is he who causes them to be, and not the inverse. Consequently, the divine nature cannot be a material thing, one that depends for its being on others. Likewise, Aquinas thinks that God is pure actuality, a plenitude of being that is transcendent and incomprehensibly perfect, and that gives being to all others, so his being is not subject to the potentiality of becoming more perfect. If he were material this would be the case, as he would be continually subject to the potency of alteration for an ameliorated state. Thus, the divine nature is not a material body.
Arguments of this kind lead Aquinas to affirm that God is simple in a way material beings are not, since he is not a composite of form and matter. We should note the principally apophatic character of this affirmation. God’s nature cannot be imagined, represented sensibly, or conceived of after the fashion of any of the material bodies that we continually experience. He is the author of the physical cosmos and is even intimately present to all he creates as its transcendent author, but he is not a material being and in this sense is unimaginable.
Evidently this understanding of God aligns closely with the biblical and patristic notion we explored above, that God is not a material body. The idea also has trinitarian consequences. If the nature of God common to all three persons is not material, then the distinction of persons in God cannot take place in virtue of a material distinction of the divine nature, as if one person were to have some composite part of the deity and another person were to have another part. Instead, one must find alternative analogies to conceive of the distinction of persons in God, based on immaterial procession, so as to think about the eternal generation of the Word and the eternal spiration of the Holy Spirit. Classically this is done by appeal to the analogy from human acts of the mind, that is to say, by conceiving of the Son analogically as the Logos or immaterial Word of the Father, who proceeds from the Father by similitude to a human act of immaterial understanding, and by conceiving of the Spirit analogically as Love, who proceeds from the Father and the Son by similitude to a human act of immaterial willing or of love (ST: q. 27 [part I]).
4.2.2 Essence and individual
The second negation of composition in God follows closely from the first. Every material thing we encounter is an individual of a given kind. A given human being, such as St. Paul, is not identical with human nature as such, but is one individual having human nature. The world we experience consists of a variety of such kinds of beings, such as humans, horses, trees, and so forth, each of which kind is instantiated not in a platonic idea, but only ever in a multiplicity of concrete individuals. Therefore, when we think of what is essential to an individual being (such as a human being) we may define the essence by reference to both the form and matter, if the latter is considered abstractly and universally, as a necessary constituent of the nature of such things. That is to say, each human being consists essentially of both form and matter, of soul and individual body, not merely of the soul. But the individual matter of Paul is not essential to any other human being, nor could it be (ST: q. 75, a. 4 [part I]; Summa Contra Gentiles [SCG]: c. 54 [part II]). It is human to have an individual body, then, but it is not essential to us as humans to have the body of another individual human distinct from ourselves. Given this way of thinking about the essences of individuals we experience in the material world, is it also then possible to think of God along these lines? Is God (the Lord God of Israel) one god among others, an individualized divine nature who shares the same nature and properties with other such beings, but who is individually distinct from the other gods?
Aquinas argues that this cannot be the case (ST: q. 3, a. 3 [part I]). God is not composed of matter and form, so he is individuated by his form alone. Otherwise stated, God is unique in virtue of his individual deity. He is the one God because he alone has the nature of God. Evidently this medieval scholastic idea aligns quite closely with the modern historical question we noted above pertaining to the development of Israelite religion. How, historically speaking, did ancient Israelites come to believe that Yhwh is the one true God? That question is genealogical and is related to ancient claims of prophetic revelation, while the question we are treating here is metaphysical, and has a philosophical dimension. Ultimately, however, the two topics are deeply related, since the genealogical question seeks to resolve the question of when and how the people of Israel came to the conviction of something like the idea formulated by Aquinas and other theologians in a more theoretical mode; namely that God alone is God, that he alone possesses the nature and attributes of the one God and Creator of all things.
This idea also has trinitarian consequences, since it suggests that if the three persons each possess the divine nature in its fullness, then they are not three individual beings, each having the divine nature in the same way three human persons have human nature, that is to say as distinct substances. Rather each has the fullness of the divine nature within his person, and thus they are each the one God, since there is no composition of nature and individual in God. The three persons are ‘consubstantial’.
4.2.3 Essence and existence
Aquinas posits a real distinction in all created beings of essence and existence (or esse in Latin) (De Ente et Essentia [DEE; see 1948]; SCG: c.52–54 [part II]; De Potentia Dei [QDP]: q. 7 [part 1] [see 1965]). Essence for Aquinas signifies the nature of a given thing. In material beings, the essence consists of both form and matter, where the latter is conceived of abstractly in universal terms. For example, it is not essential to all human beings to have the body of a given individual like Paul, nor could it be, but it is essential to all human beings to have a physical body as well as a soul. Therefore, the whole form-matter composite pertains to the essence of what it is to be human. In angelic realities, which are wholly immaterial, the essence pertains to the form alone, as each angel has a unique nature in virtue of its immaterial form, and not in virtue of an immaterial body.
Esse signifies the act of being, or singular existence, of a given individual substance (DEE: c.2, 5; QDP: q. 7, a. 2, ad 9). Each individual material essence (a human being or a horse or a tree) has an individual existence. This is true as well of each immaterial being (or angel); its existence is unique. Existence is thus common to all things in a way essence is not, since the many created realities in the world are of many different natural kinds (essences), but they all have existence in common. At the same time, existence is proper to each individual reality in a wholly unique way, as the singular existence of the archangel Gabriel is distinct from that of a man, a pine tree, or a blade of grass. No created reality is the cause of its own existence. Instead, we see that all realities around us, including ourselves, come into and can go out of existence, and they are both given existence and sustained in being due to the causal activity of others. Nothing in creation exists merely by nature, due to the kind of essence it has, such that it would exist by sheer primal necessity. Aquinas famously relates essence and existence in creatures to one another as potency is related to act. Each individual essence can be or not be, and thus is either in mere potency to exist or does truly exist. However, even when creatures do actually exist, they have the latent potency within them not to exist, in virtue of their created status.
Aquinas argues that this kind of composition of essence and existence that is found in all created realities cannot obtain in God or his divine nature (ST: q. 3, a. 4 [part I]). In differentiation from creation, God the Creator does not receive his being from another and is not caused to be. He simply is from all eternity and is the cause of all else that is. He communicates existence to others, from the abundance of his own infinite and perfect being, but his being is not received from, ontologically enriched by, or dependent upon, his interactions with his creatures. If this is the case, then God is incomprehensibly different from his creation. His divine essence alone exists by nature and is ontologically necessary in a way no created reality can be. His essence also contains the plenitude of all existence, since he is being essentially, in all that pertains to being, and all that comes to exist in creation comes from his prior actuality and perfection, and is a merely participated and imperfect expression of God’s transcendent nature (ST: q. 13, a. 11 [part I]). In God there is no ontological composition of essence and existence.
Evidently this idea is deeply related to the Old Testament notion we touched upon above, regarding the idea that the God of Israel alone is the Creator of all that is, ‘he who is’, (Exod 3:14–15; Isa 45; John 8:58) the one who gives being to all things. It also touches upon the idea in trinitarian theology that the Father, Son, and Holy Spirit each possess the plenitude of divine esse, and that they all therefore give rise together to all that exists apart from God. In short, all acts of the Holy Trinity ad extra (‘outside’ of God) in the creation and the redemption, are works of all three persons, since all three possess the one essence of God and thus the one divine existence (ST: q. 42 [part I]). They each possess that plenitude from which all things proceed and come forth in being, and by which all things are sustained in being. On this view, which is related logically to the doctrine of divine simplicity in the aforementioned respect, it is the Trinity that creates, sustains, and redeems all things in creation, and never merely one of the persons acting alone, as if the Father might act divinely as God and Lord, without the Son or the Spirit. The unity of trinitarian action and the doctrine of divine simplicity are deeply interrelated ideas (ST: q. 11, a. 3 [part I]).
4.2.4 Substance and accident
The final composition we will consider in this context pertains to substance and accidental property. As Aquinas notes, created realities are complex ontologically, since they are each composed of substance and accidents. That is to say, they have unity as individual substances (like a singular tree or a human) and they also have properties such as a given quantity, qualities, relations to other things around them, and so forth. Human qualities such as intelligence or moral excellence are not identical with the whole human substance (as if a person were their act of understanding or volition), but characterize human beings as important properties.
Following Augustine, Aquinas argues that this kind of ontological composition does not exist in the divine nature (ST: q. 3, a. 6 [part I]). One reason has to do with act and potency argumentation. A given substance that has accidental qualities is in ontological potency to have or not have the qualities in question, especially if these qualities emerge and develop dynamically. The divine nature however is not in potency to further development through a historicity of divine becoming and does not depend upon any other reality causally so as to develop in being (for example, through interaction with creation). Instead, what we call God’s ‘essence’ entails a numinous plenitude such that God is perfect in being from all eternity to all eternity (ST: q. 4 [part I]). A similar argument follows from the negation of the real distinction of essence and existence in God. If God possesses essentially, or by nature, the fullness of existence, and communicates being to all others as Creator, then God does not develop in existence progressively, as he would if he had something like the equivalent of accidental properties as they are found in human beings (ST: q. 3, a. 6 [part I]).
On this view, we may still affirm (along with Aquinas and other like-minded medieval theologians) that God actively knows and loves all that exists in the creation. Indeed, Aquinas argues at length that all that exists in creation comes forth into being from the knowledge and love that characterize the divine essence (ST: qq. 14, 19, 20 [part I]). Nevertheless, such knowledge and love of the divine nature are not like human understanding and loving, at least in this, that they are not enriched or historically qualified positively in a developmental fashion by engagement with creation. Rather, God creates out of the plenitude of eternal contemplation and love that characterizes his very nature as God (ST: q. 14, a. 8 and q. 20, a. 2 [part I]). Were this not the case and were God to learn experimentally from creation and grow in moral virtue through his engagement with it, then creation would in some sense actively qualify and cause God to be, and the two would necessarily exist within a larger co-constituting system, an idea that stands in tension with traditional biblical and patristic notions of Creator and creation.
As we have noted above, Augustine argues in a similar vein that God is not wise or good by qualification but that God is his goodness and wisdom. This idea has consequences for trinitarian theology in several ways. First, it means that one cannot differentiate the persons in God by appeal to distinct natural characteristics, as if God were powerful only in his paternity, wise only in his filiation, and good only in his spiration. Instead, all three persons partake of the plenitude of the divine essence and therefore also partake of the plenitude of all divine ‘qualities’, which are mysteriously identical with the essence of God (ST: q. 42, aa. 1 and 4 [part I]). The Father, Son, and Holy Spirit possess in equal and identical measure the power, wisdom, and goodness of God that characterize his essential life (ST: q. 39, aa. 7–8 [part I]). Second, the divine attributes, such as wisdom and goodness, must also be in some real sense identical with one another. What we perceive in creation as distinct features of human beings, such as knowledge and love, can and must be ascribed to the divine nature, but what we signify when we indicate them in God is something that is mysteriously one in God himself (ST: q. 13, aa. 2 and 4 [part I]). The divine simplicity, perfection, goodness, eternity, power and so forth, are identical in God, yet each of these terms helps us indicate more clearly what God is, even if his essence remains beyond our plenary comprehension. Finally, on this view, the persons in the Trinity cannot be distinguished by various qualities or accidental properties they acquire due to their respective actions in the economy of creation and salvation (this viewpoint contrasts notably with Rahner 2001: 24–30). For example, the Father is not differentiated from the Son by his unique qualifying action of creation while the Son is differentiated by his unique action of redemption or incarnation. Rather, the divine persons are at the origin of all that occurs in the economy of creation and they act in virtue of the essence they share as the one God. That action does not re-qualify or enrich them collectively or individually but is the expression of the plenitude of trinitarian life that they possess inalienably from eternity.
4.2.5 Trinitarian persons and divine simplicity
Aquinas’ theology of divine simplicity has a direct bearing on the way in which he conceives of the distinction of trinitarian persons. If the three persons are each the one God and subsist as the one God, then the real distinctions that obtain between them do not derive from the divine nature which they share but from the two processions of generation and spiration and from the relations of origin that these processions instantiate. The Father eternally begets the Son as his Word, and in so doing communicates to the Son all that he is and has as God (ST: q. 27, a. 2; qq. 33–34 [part I]). The Father and the Son eternally spirate the Holy Spirit as their reciprocal Love, and in so doing communicate to the Spirit all that they have and are as God (ST: q. 27, aa. 3–4; qq. 36–38 [part I]). The Son is thus related to the Father eternally as the one he originates from, and the Spirit likewise to the Father and the Son. Like other scholastics, such as Albert the Great and Bonaventure, Aquinas argues that the relations of origin in the Holy Trinity are not accidental properties of the persons but are mysteriously subsistent (ST: q. 29, a. 4 [part I]; Bonaventure, Commentaria in Quatuor Libros Sententiarum: d. 26, a. un, q. 3; Emery 2001: 455–465). The Father is his paternity; he is a principle of origin of the Son and the Holy Spirit in all that he is, as font of the trinitarian life. The Son is his filiation; he is from the Father and for the spiration of the Spirit in all that he is as Word. The Spirit is his spiration; he is a from the Father and the Son in all he is (ST: q. 33, a. 2 [part I]). Each person is truly God (having in himself the plenitude of the divine essence) and each person possesses his deity in a particular personal mode. He is God in either a paternal, filial, or spirated way (Emery 2005: 31–77). Such notions follow directly from the two-fold affirmation that (1) the divine essence is simple in the ways indicated above and (2) the three persons are one in essence (consubstantial, homoousios), in accord with the formulation of the Nicene creed (Emery 2000: 521–563).
This view of the trinitarian persons underscores both the relational primacy of the Father and the radical egalitarianism that obtains in God. The Father is the principle and font of trinitarian life, but he is not greater in nature or ontological stature than the Word or the Spirit, even if these two derive from him originally. Indeed, they receive eternally from him all that he is as God, in the simplicity and plenitude of his divine being and life. This affirmation does not negate or eclipse the real distinction of the persons in God or the interpersonal reality of their communion or their relationships with creatures, by grace. On the contrary, this way of indicating personal distinction in God augments a sense of their communion as mutual indwelling. The interpersonal communion of the Trinity implies a singular, shared, mutual essence of the one God present in all three persons (ST: q. 42, a. 5 [part I]). This means that by perichoresis, or mutual indwelling, the whole of ‘what’ the Father is, is in the Son and the Spirit, and the whole of what the Son is, is in the Father and the Spirit, and the whole of what the Spirit is, in his divine plenitude, is in the Father and the Son. This mutual indwelling is also accomplished from and in the living and eternal ‘cycle’ of trinitarian processions, so that the Father is in the Son and Spirit insofar as he communicates to them to be from him all that they are as God, yet in personal distinction. They likewise only have in themselves all that the other two do, either as one who receives all that he is from the Father and gives it to the Spirit with the Father (in the case of the Son), or as one who receives all that he has from the Father and the Son (in the case of the Spirit).
The distinction of persons in their self-communication to creatures by grace is also underscored by this doctrine of divine simplicity since it allows one to appreciate that when all three persons each act distinctly, they also always act with the other two. All actions of the Father, while paternal in mode, also imply common action of the Son and Spirit respectively, who act in their own irreducibly distinct personal modes of action. When one person is active in his distinctness, the other two must also be active in their relative modes of distinctness. If the Father communicates grace to a human person, in his distinctive mode as Father, then the Son also does so with him, in his distinctive mode as the begotten Son of the Father, and the Spirit in his distinctive mode as the spirated Love of the Father and the Son. Each person is truly God so that when we commune by grace with Jesus Christ, who is the Son of God, we also commune with one who, as God and Lord, is in perfect communion with the Father, indeed one in being with the Father, in the sense just indicated. In other words, communion with one person is always communion with that person in his personal action but it is also communion with the other two persons in their personal action, so that the reciprocity of interpersonal relationship with one person of the Trinity that grace effectuates in us, implicates personal relationship with the whole Trinity, as a communion of persons, and without conceiving of the latter in any way as a mere abstract essence.
4.3 Alternative medieval concepts
As noted above, the treatment of divine simplicity in Western medieval scholasticism is far from homogeneous. Although Aquinas’ conception of divine simplicity has been historically influential, alternative conceptions exist that have had similarly important influence in the Western theological tradition. Though they are each Franciscans, the distinctive and in some sense incompatible conceptions of John Duns Scotus and William of Ockham each deserve particular consideration in this respect.
Duns Scotus’ conception of divine simplicity can be helpfully contrasted with that of Aquinas in two ways. First, Duns Scotus posits, in keeping with Augustine and Aquinas, that God’s essence and nature is simple, in the sense that it is non-composite and individually unique. However, he retains what has come to be called ‘a formal distinction’ of the attributes of the one God. Aquinas held that our diverse ways of indicating God through divine names or attributes is semantically meaningful since each name denotes something true about God. Terms such as divine wisdom, goodness, justice, mercy, and so on, each say something true of God. However, these terms denote what is truly one and identical in God’s own essence, not formally or essentially distinct. What we call God’s wisdom, goodness, justice, and mercy are truly one in God’s own life and nature (ST: q. 13, aa. 2–4 [part I]). Duns Scotus, meanwhile, predicates these terms to God while underscoring that the attributes they specify in God are formally distinct, and not reducible to one another specifically in the eternal life of God. He does not predicate that they are accidental to one another, nor does he claim that they are properties of the essence. Like Augustine and Aquinas he denies this kind of composition in God, but his notion of simplicity is more ‘complex’ than that of Aquinas because he believes that the language we use for God’s essence when we employ terms for God must correspond in a partially univocal way to the very reality of God’s essence, and since we use distinct terms and each is posited univocally and truly of God in some sense, these distinctions in speech must correspond to something formally distinct in the nature of God (Duns Scotus, Ordinatio [Ord.]: 220.127.116.11, nos. 192–193 [in Opera Omnia: 261–262 [vol. 4]]; Cross 2005: 107–111, 235–240). Duns Scotus wants to underscore the harmony between our way of speaking of God and the very nature of God that we denote rightly in our speech.
This view of simplicity has significant consequences in Duns Scotus’ treatment of the trinitarian persons. Unlike Aquinas, who seeks to distinguish the persons of the Trinity primarily by reference to their relations of origin, Duns Scotus distinguishes the persons in part by recourse to the notion of distinct eternal natural actions of the person of the Father. Insofar as the Father naturally produces thought, through the essential activity of understanding, so he produces an immaterial Word (analogous to a concept) that is his natural offspring. This Word is infinite in perfection and consequently is a personal reality (since any reality that is infinite in perfection must be personal). Insofar as the Father naturally loves, through the essential activity of loving, he spirates the Spirit who is Love. This Love is infinite in perfection and consequently is a personal reality. The formal distinction of understanding and love that is applicable to God according to the distinction of attributes of the divine essence thus plays an important role in trinitarian theology. The Father is characterized by formally distinct natural actions that produce distinct persons. The logic of Duns Scotus’ position permits him to claim overtly that once one has identified the formally distinct attributes of the essence of God, and the naturally distinct operations that they imply, which are infinite in perfection, one can in turn demonstrate rationally by philosophical argument that there are eternal personal processions in God of Word and Love. While Aquinas argues that natural reason cannot demonstrate the existence of the Trinity as the mystery of the inner life of God (and so this has to be revealed to be known), Duns Scotus argues that there is some real possibility of natural knowledge of the trinitarian processions, based on his doctrine of formal distinction, and his mitigated reception of the doctrine of divine simplicity (Duns Scotus, Ord.: 18.104.22.168–4, nos. 221–222, 226, 355–356 [Opera Omnia: 259–263, 336 [vol.2]]; Cross 2005: 132–142, 153–155). Duns Scotus’ theology thus appears less apophatic than that of Aquinas, suggesting a marked confidence in the natural dispositions of human reason to attain understanding about God’s inner life as Trinity, as reflected both in the doctrine of univocal divine names and the theory of formal distinction.
Ockham’s position on divine simplicity is in many respects the inverse of Duns Scotus’. Ockham posits that there is such a marked notion of divine simplicity that obtains when one thinks of God that it is difficult to entertain the very notions of eternal processions and distinction of persons in God. If God is simple, how can God be understood as a Trinity? Ockham problematizes the traditional Augustinian notion of a ‘psychological similitude’ that conceives of the two processions of the Word and Spirit by comparison to human mental acts of understanding and love, respectively. This similitude is not intelligible for Ockham, in light of the doctrine of divine simplicity, except as something akin to a metaphor (Ockham, Ord.: d. 2, q. 1 [Opera theologica [oTh.]: d. 1, q. 6 [vol. 2]; oTh.: d. 7, q. 2 [vol. 1]; oTh. [vol. 3]; Friedman 2010: 124–131). The reason is that everything that is found in one divine person is found in another, if they are truly one in essence, and the activities of understanding and will are proper to each person so they cannot be distinguished by such activities. The Church affirms that there is a distinction of persons in God according to relation of origin, and so Ockham derives a way to affirm nominally a set of propositions about the Trinity that are logically consistent. He is reticent, however, about our capacity to attain to any true knowledge of the eternal processions of the Trinity in this life (whether analogically or univocally). This reservation is related to his notion of divine simplicity.
Another alternative is presented by the fourteenth-century Byzantine theologian, Gregory Palamas, who distinguishes between the essence and energies of God. This distinction has applications in Gregory’s theology of grace and divinization. By God’s gift, human beings are invited to participate in the energies of God, but they are not able to apprehend or to enjoy any immediate spiritual communion with his essence, even in heaven. They do participate in the life of God in himself, but under a condition (see Gregory Palamas, The Triads: 93–112). This view is influential with some Eastern Christians and can be associated logically with those who are critical of the Filioque, the affirmation of the procession of the Spirit from the Father and the Son. Some Western theologians like Augustine, Anselm, and Aquinas (in differing ways) distinguish the Son from the Spirit based on relations of origin, and so they underscore that there must be a relation of origin of the Spirit from the Son. Eastern theologians inspired by Palamas, who posit a highly qualified concept of divine simplicity, may accept the Cappadocian notion of the generation of the Son from the Father and of the procession of the Spirit from the Father without feeling constrained by the Western concept of the doctrine of simplicity to resolve the question of the relation of the Son to the Spirit (the relation of origin between them) (see Papademetriou 2004: 77–94). Therefore, they may argue that the absence of distinction between essence and energies in Western theology (and the corresponding notion of God’s essence as non-composite) is logically related to the Western affirmation of the Filioque. Furthermore, some argue (paradoxically) that the Western concept of simplicity leads to pantheism, since it somehow implies that God’s essence is identical with his energies, and thus God is identical with his activity in the world (see Lossky 1997: 73–75). This latter claim seems to brazenly ignore clear conceptual arguments to the contrary.