I. St. Thomas on Divine Ideas

Following St. Augustine, St. Thomas says that the Greek term ‘idea’ should be translated into Latin as ‘form or species’ (forma vel species).Footnote ⁷ By form, we should not understand some intrinsic form, as the soul is the form of human beings. Instead, by ‘idea’ is understood a separate form toward which something is formed, and this is an exemplar form to whose imitation something is constituted.Footnote ⁸ Such constituting can occur in two ways. In one way, as when a form is the principle of cognizing the thing. In another way, as when a form is the exemplar guiding the production of a thing.Footnote ⁹ Divine ideas are forms in both ways and play both a cognitive role and a causal role in St. Thomas's theory.

Since ideas play both a cognitive role and a causal role, we are led to ask whether the ideas are principles of speculative cognition or practical cognition. St. Thomas argues that speculative and practical cognition is threefold according to its end. Knowledge can be either purely speculative, purely practical, or partially practical and partially speculative. Things the knower cannot bring about are purely speculative. God knows himself and evil, but he cannot cause himself, and he does not cause evil. Thus, his knowledge of them is speculative. Things the knower does bring about are simply practical. God has practical knowledge of anything that he creates. Between these two extremes are the things that the knower could bring about but does not. When a builder examines the individual parts of a house that cannot exist without each other or considers the house as a whole without ordering that knowledge to operation, his knowledge is partially speculative and partially practical. He considers something that he can make, but not insofar as he can make it. Everything God could create but does not falls into this category.Footnote ¹⁰

St. Thomas then correlates the two roles of divine ideas with his discussion of speculative and practical cognition. This correlation results in the distinction between two types of ideas. Insofar as they play a causal role, divine ideas are called ‘exemplars,’ and they pertain to practical cognition. Exemplars are ideas according to which God will create something at some time. Insofar as they play a cognitive role, they are called ‘reasons’ (rationes) and pertain to speculative cognition. God has rationes of anything he could create regardless of whether he creates it.Footnote ¹¹ Having made this distinction, St. Thomas emphasizes the causal role. Strictly speaking, the term ‘idea’ refers only to the exemplars according to which God actually produces creatures. Ideas are called rationes only in a broad and extended sense.Footnote ¹²

Having determined that an idea is primarily an exemplar, Thomas argues that there are many divine ideas. His argument for this position is taken from final causality. What the principal agent properly intends in any effect is the ultimate end, as an army's order by the general. That which is best in existing things is the good of the universe's order, as is obvious from Aristotle's Metaphysics XII. Therefore, God properly intends the order of the universe. However, if the universe's very order is per se created by him and intended by him, he must have an idea of the universe's order. The ratio of any whole cannot be had unless the proper rationes of the parts from which the whole is composed are also had, as the builder could not conceive the house's species unless he had the proper ratio of each of its parts. Therefore, there must be proper rationes of all things in the divine mind.Footnote ¹³

Realizing that his conclusion seems contrary to divine simplicity, Thomas immediately explains that this plurality is not repugnant to simplicity. A form in the intellect can exist in two ways. First, it is a principle of the act of understanding. This form is a likeness of the thing understood in the intellect. A form as principle makes the intellect be in act. God's only form as principle is his essence. Thus, his wisdom and art are one.Footnote ¹⁴ Second, a form is the term of the act of understanding, as when the builder thinks out (excogitat) the form of a house through understanding.Footnote ¹⁵ God has many forms as terms.

God perfectly cognizes his essence; that is, he cognizes it according to every mode by which it is cognizable. The divine essence can be cognized not only as it is in itself but also as it can be participated by a creature according to some mode of likeness. Each creature has a proper species according to which it participates a likeness of the divine essence in some mode. Therefore, insofar as God cognizes his essence as it is imitable by such a creature, he cognizes his essence as the proper ratio and idea of this creature. The same is true for every creature. Thus, God understands the proper rationes of many things, which are many ideas.Footnote ¹⁶

This response is noteworthy for several reasons. First, it emphasizes that the divine ideas are posited because God must know what he creates. It would be imperfect for him to know what he creates only in a general way. If God is to understand the whole perfectly, he must know how the parts contribute to the whole. If he only knew the whole, God would only know the parts indistinctly and under some confusion.Footnote ¹⁷ In short, God would be as Averroes described; he would have only indeterminate knowledge of things other than himself.Footnote ¹⁸ He would be in potency, rather than perfect act. Second, St. Thomas emphasizes that ‘an idea does not name the divine essence insofar as it is an essence, but insofar as it is a likeness or ratio of this or that thing.’Footnote ¹⁹ When God knows his essence, he knows himself perfectly, and he knows all the ways his essence is imitable by creatures as secondary considerations. His understanding precedes any of these creatures' existence and so is not caused by any of them. It causes them instead.Footnote ²⁰ The many respects in which God knows himself as imitable are in God, not creatures, but they are not real respects like the respects distinguishing the persons of the Trinity. Instead, they are rational respects understood by God.Footnote ²¹

II. The Summa Contra Gentiles

Divine ideas are conspicuously absent from the Summa Contra Gentiles. There is even irrefutable manuscript evidence that divine ideas were present in earlier drafts of the Summa Contra Gentiles, and Aquinas removed them in the final redaction.Footnote ²² This evidence seems to support the view of those who believe that that divine ideas add nothing to the discussion of divine knowledge.Footnote ²³ A close look at the order of the Summa Contra Gentiles' text and its arguments, however, reveals that the substance of Aquinas's theory of divine ideas is present, even though he does not call them ‘divine ideas.’ The language of ‘divine ideas’ is absent, but the teaching is not.

Before delving into St. Thomas's arguments from the Summa Contra Gentiles, some comments on the division of questions are in order. Summa Contra Gentiles I, cc. 44–77 is St. Thomas's most extended discussion of divine knowledge. For the most part, these chapters treat the questions concerning God's knowledge in the same order as St. Thomas treats them in his other ex professo works. A notable exception to this similarity is cc. 51–54.Footnote ²⁴ The order of Aquinas's presentation in Summa Contra Gentiles I, cc. 49–57 and Summa theologiae I, q. 14, aa. 5–7 differs. In Summa Contra Gentiles I, cc. 49–50 and Summa theologiae I, q. 14, aa. 5–6, St. Thomas argues that God knows things other than himself with a proper cognition. In the Summa theologiae, Aquinas immediately asks whether God's knowledge is discursive in a. 7. However, in the Summa Contra Gentiles, he delays the question of discursive knowledge until chapters 55–57.Footnote ²⁵ Between c. 50, and c. 55, St. Thomas takes a detour to ask how God can know a multitude of objects.

At first glance, this detour does not seem to fit in the progression of the inquiry. Aquinas begins c. 50 by pointing out Avicenna's error that God only has universal cognition of things other than himself, i.e., he knows them only insofar as they are beings. He spends the rest of the chapter arguing that God cognizes all other things as they are distinct from each other and God.Footnote ²⁶ Admittedly, arguing that God has distinct knowledge of things other than himself is not the same as explaining how God has such distinct knowledge, but some of the arguments in c. 50 seem to answer the latter question too.

Given this argument, the answer to how God knows a multitude of things seems clear. He knows them because all their proper forms are in him. Thomas offers a similar argument in Summa theologiae I, q. 14, a. 6, and proceeds directly to the question of discursive knowledge.Footnote ²⁸ Why does he proceed directly to the question of discursive knowledge in the Summa theologiae, but feels compelled to offer more arguments explaining how God knows a multitude of things in the Summa Contra Gentiles?

I submit that Thomas's progression of questions differs in the Summa Contra Gentiles because he has divine ideas in mind. Thomas announces at the beginning of Summa theologiae I, q. 14 that he will treat the divine ideas in its own question.Footnote ²⁹ Thus, he delays his full explanation for how God knows a multitude until q. 15. Since the Summa Contra Gentiles makes no such announcement, Aquinas must account for how God knows many things immediately after he argues that God distinctly cognizes everything. It is not enough to say that the proper forms of everything preexist in God. By itself, this claim merely delays the explanation of how God knows many things because it leaves unexplained how the proper forms of everything preexist in God. Aquinas must explain the metaphysical structure of this preexistence especially because it is not apparent why such a plurality of forms is not contrary to divine simplicity.

As a result of this obligation, Thomas proceeds in Summa Contra Gentiles I, cc. 51–52 to investigate various ways to understand the multitude of intellectual objects in the divine mind. Many of them are problematic. If each thing understood had a distinct being in God, God's essence would be a certain multitude, or it would undergo addition such that there would be accidents in God. If these intelligible forms exist in themselves as Plato supposed, then God would be in potency and consult another to gain knowledge.Footnote ³⁰

These solutions are contrary to the simplicity and perfection of Ipsum Esse Subsistens, so St. Thomas proposes in c. 53 that we diligently inspect how things understood exist in the intellect. When we know external things, the thing understood does not exist in our intellect according to its proper nature. We need a species in our intellect that is simultaneously a likeness of the thing known and the principle of our understanding, making our intellect actual.Footnote ³¹

In addition to the intelligible species, the intellect forms a certain intention of the thing understood, which is its ratio, which the definition signifies. This process is necessary because the intellect is indifferent to the presence or absence of the thing. The intellect understands the thing as separate from material conditions, without which conditions the thing does not actually exist (in rerum natura non existit). The separation could not occur unless the intellect formed an intention for itself. Since it is a quasi-term of intelligible operation, this intention is other than the intelligible species that makes the intellect be in act. Both the intelligible species and the intention are likenesses of the thing. However, the intelligible species is the principle of intellectual operation, and the intention is the term of intellectual cognition. The intellect can only form an intention of the thing because the intelligible species is a likeness of the exterior thing. Moreover, because the intention is like the thing, it follows that the intellect forms the intention in order to understand the thing itself.Footnote ³²

Turning to the divine intellect, St. Thomas notes that it understands no other species than its essence. Moreover, the divine essence is a likeness of all things. Thus, it follows that the conception of the divine intellect, as it understands itself, which is its Word, is a likeness of God himself understood and of all the things of which the divine essence is a likeness. Therefore, through one intelligible species, which is the divine essence, and through one understood intention, which is the Divine Word, God can understand many things.Footnote ³³

Having argued that the supremely simple divine essence is the likeness of all intelligible things through his one intention in c. 53, St. Thomas argues in c. 54 how this likeness is possible. He begins by noting that this problem is challenging: ‘it can seem difficult or impossible to someone that one and the same simple thing, like the divine essence, is the proper ratio or likeness of diverse things.’Footnote ³⁴ The problem still lingers, and, as Msgr. John Wippel notes, ‘unless we resolve this, we may conclude that God has only a general or universal knowledge of things.’Footnote ³⁵ Aquinas continues, the divine intellect comprehends in itself the perfections (nobilitates) of all beings, not through composition, but through perfection. Every form, whether proper or common, is a certain perfection. It does not include imperfection except as it falls short of true being (esse). Therefore, the divine intellect can comprehend what is proper to each thing in its essence by understanding how each thing imitates the divine essence and the way each thing falls short of the divine essence. Thus, by understanding his essence as imitable through the mode of life and not the mode of cognition, God has the proper form of a plant. Furthermore, if he understands his essence as imitable through the mode of cognition and not the mode of intellect, he has the proper form of an animal. The same follows for the other modes.Footnote ³⁶

From this argument, he says, it is clear that the divine essence, insofar as it is absolutely perfect, can be had as the proper ratio of singulars, and God can have proper cognition of them all. Since the proper ratio of one thing is distinguished from the proper ratio of another, and distinction is the principle of plurality, it is necessary to consider a certain distinction and plurality of rationes in the divine intellect. Consequently, since this obtains according as God understands the proper respect of assimilation that each creature has to him, it follows that the rationes of things in the divine intellect are not many or distinct except insofar as God cognizes things to be assimilable to him in many and diverse ways. St. Thomas concludes the chapter by noting that this reasoning is what St. Augustine had in mind when he said God makes man and horse according to different rationes and that things' rationes are many in the divine mind. Moreover, in some way, this reasoning saves Plato's opinion of ideas, according to which opinion all things that exist in material things are formed.Footnote ³⁷

Thomas's solution that God's simple essence is the proper ratio or likeness of all intelligible things relies on a distinction parallel to the one we saw above between form as principle and form as term. The divine essence is the only intelligible species for the divine intellect, i.e., its only principle. From this one intelligible species, the divine intellect ‘forms in itself a certain intentio of the thing understood, which is its ratio, which the definition signifies.’Footnote ³⁸ The intentio seems to serve the same role as the form as term. God has one intentio that entails many rationes. But why does Thomas use a new term when he could have used the distinction between an intelligible species as principle and an intelligible species as term as he did in the analysis above?Footnote ³⁹ What does intentio add that intelligible species as term does not?

This answer to this question can be found in Aquinas's discussion of the eternal generation of the Divine Word in Summa Contra Gentiles, IV, c. 11. He argues that intellectual life has various levels of perfection corresponding to diverse degrees of potency in self-knowledge. Intellectual life is the supreme and highest grade of life because it reflects upon itself and can understand itself. Among intellectual lives, God's intellectual life is the highest because his understanding is not other than his esse. Thus, his understood intentio is the divine essence itself. Aquinas then defines an understood intentio as ‘that which the intellect conceives in itself of the thing understood.’Footnote ⁴⁰ In man, an understood intentio is neither the thing understood itself nor the substance of the intellect itself. Instead, it is a certain conceived likeness of the thing. The understood intentio names an interior word that is signified by an exterior word. An intentio is “the intelligible content (ratio) of the thing, which the definition signifies.”Footnote ⁴¹ An intention is the term of the intellect's understanding. Thus, Thomas distinguishes an intentio from an understood intentio: ‘it is apparent that understanding the thing is other than understanding the understood intention itself, which the intellect makes when it reflects upon its work.’Footnote ⁴² An intentio is the product of a direct act of understanding, and an understood intentio is formed by intellectual reflection. The latter appears when the intellect looks back upon its work.

In God, since his esse and understanding are the same, the understood intentio is the same as his intellect. Moreover, because his intellect is the thing understood when he understands himself, he understands all things. When God understands himself, his intellect, the thing understood, and the understood intentio are the same.Footnote ⁴³ And since what is understood qua understood must be in the intellect, God must be in his understanding qua understood. What is in the understanding is an understood intentio and word. Thus, by God's self-understanding, the Word of God is begotten.Footnote ⁴⁴

Thomas justifies his claim that the Word of God is begotten by God's self-understanding by identifying the being of a word interiorly conceived with an understood intentio. As with his understood intentio, the being of God's interiorly conceived word is the very act of being understood. An interiorly conceived word, then, is a certain ratio and likeness of the thing understood. This is as true for the Word of God as it is for a mental word conceived by a human intellect. When the interior word is a likeness of another as the principle of that other, it is an exemplar. When the interior word is a likeness of another as to a principle, it is an image. The likeness existing in the artist's mind is both the principle of his operation and his artwork's exemplar. Since God's self-understanding is the principle of all things understood by him (by intellect and will), and since the principle of all things understood by God is the Word of God, that Divine Word is compared to all things understood by God as an exemplar.Footnote ⁴⁵

Several conclusions follow from this explanation of intentio. First, an understood intentio is not merely the thing understood. It is conceived in the intellect as an act of reflection upon the thing understood. The thing understood by God is his essence, i.e., himself. By a certain reflective act, as it were, God then forms the understood intentio and rationes of all the things that can have a likeness to his essence. These likenesses can, by an act of will, be exemplar causes. Since there are many ways of being like the divine essence, there are many rationes. Second, a divine understood intentio, which must be in the Word of God, is the exemplar of whatever God wills (or could will) to create. The rationes of all things are in God as in an exemplar cause, and they only exist because they were first in God's understood intentio.

From these two conclusions, we should say that Aquinas's theory of divine rationes in the Summa Contra Gentiles is only linguistically different from his theory of divine ideas in other texts. The rationes in the divine intellect are the exemplar causes of everything that comes forth from God. Thus, as Wippel says, Aquinas's ‘defense of a plurality of divine reasons for individual creatures is equivalent to a defense of a plurality of divine ideas.’Footnote ⁴⁶ The fact that he uses the word ‘ratio’ instead of ‘idea’ is of little consequence. St. Augustine argues that ‘ratio’ is not an excellent translation for the Greek term ‘idea’ because ‘ratio’ is primarily used to translate logos. However, he admits that whoever wants to use ratio still gets the same message across. St. Augustine even uses the term ratio in addition to the terms idea, forma, and species to explain the divine ideas.Footnote ⁴⁷ St. Thomas, too, has seen fit to describe divine ideas using the less accurate—but still appropriate—term ratio.

III. The Absence of Divine Ideas in the Summa Contra Gentiles

If Aquinas's theory of divine rationes in the Summa Contra Gentiles is, in fact, a theory of divine ideas, why would he switch to the less appropriate term? Scholars have offered several suggestions for this change. Louis Geiger argues that Thomas had been utilizing the more Aristotelian vocabulary of intelligible species. So, he sticks to a more Aristotelian expression when he needed to account for a distinction between the species as actualizing form and the object known.Footnote ⁴⁸ Wippel holds that Thomas does not speak of ideas because his primary concern in that section of the Summa Contra Gentiles is to show how God can know many creatures without compromising his unity and simplicity. He is concerned with the cognitive role only, not the causal role. As we saw in the first section, Aquinas thinks that strictly speaking, divine ideas perform the causal role as exemplar causes. Thus, it is not surprising that he would choose a term other than ‘divine idea’ since he only speaks of the cognitive role.Footnote ⁴⁹ Vivian Boland concurs with Wippel's analysis, and he adds that Thomas became more sensitive to divine simplicity and Aristotle's critique of Plato's theory of ideas. The presence of the term ‘idea’ in prior editions of I, c. 54 ‘perhaps seemed too platonic.’Footnote ⁵⁰ Aquinas did not feel the need to save the word ‘idea’ since he could express the same theory with the term ratio.

Gregory Doolan also reaffirms Wippel's reasoning, and he adds that the use of the word ratio is crucial for understanding the sort of plurality that Thomas wishes to attribute to the divine ideas. The multiplicity of divine ideas is a multiplicity according to reason, not according to reality, i.e., a logical multiplicity. Thus, ‘it might be tempting to dismiss this multiplicity as merely logical and, hence, of no philosophical significance.’Footnote ⁵¹ We should not give in to this temptation. The plurality of ideas is rooted in the ontological reality that the divine essence can be imitated in many ways.Footnote ⁵² The multiplication of rationes in God is no human invention. It precedes all creation and accounts for the distinction in things: ‘there is a plurality of natures in things only inasmuch as there is first a plurality of ideas in God.’Footnote ⁵³ The choice of ratio over ‘idea’ emphasizes this point. Not only does a multiplicity of rationes not contradict divine simplicity, but it is also necessary if God is to know a multitude of objects.

These reasons are good, but I would like to add one more possible explanation for omitting the word ‘idea’ in the Summa Contra Gentiles. Thomas might not have included a systematic treatment of divine ideas because it would not have been as conducive to the work's purpose. Unlike his other works, the Summa Contra Gentiles has a more apologetic aim.Footnote ⁵⁴ The work is meant to promote the truth of the Catholic faith by removing contrary errors. Since many of these errors are held by Muslims and pagans, who do not admit the authority of Scripture, it is necessary to have recourse to the common authority of natural reason.Footnote ⁵⁵ Thus, the Summa Contra Gentiles' first three books are explicitly philosophical and refer to Scripture only in passing at the end of some chapters.Footnote ⁵⁶ Since reason falls short of some divine truths, such as the fact that God is three and one, philosophical reasoning cannot demonstrate such truths.Footnote ⁵⁷ As a result, Thomas says that his intention is not so much to convince his interlocutor by overwhelming arguments as it is to resolve the arguments that his interlocutor has against the truth.Footnote ⁵⁸ Whenever the truth of the matter is only available by faith, it is sufficient to show that the Christian position is not contrary to reason. If it were contrary to reason, then it would have to be false. If it is consistent with reason, then it cannot be rejected out of hand.

At first glance, this apologetic explanation may seem unhelpful because the divine ideas are not beyond philosophical speculation. Divine ideas are a properly philosophical subject of inquiry because they are exemplar causes. It would have been philosophically appropriate for Aquinas to include divine ideas in his discussion in the Summa Contra Gentiles. Nevertheless, I do not think that including divine ideas would have been more conducive to his goal.

Dialogue is always best served when the parties agree upon their terms. Thomas names Muslims and pagans as some of his dialogue partners in the work. He has in mind the pagan, Aristotle, the Muslims, Avicenna and Averroes, and their intellectual descendants. This fact matters for two reasons. First, the way that Christians use the term ‘ideas’ is foreign to his interlocutors.Footnote ⁵⁹ If he wants to uproot his interlocutors' errors and replace them with the truth, why would Thomas introduce a foreign vocabulary into the work? To speak in such jargon would not be conducive to his project. His interlocutors (at least in their Latin translations) are comfortable speaking in terms of intentio.Footnote ⁶⁰ Aquinas uses this terminology in SCG I, c. 53, and tells the reader that the understood intention of the thing is the thing's ratio, which the definition signifies.Footnote ⁶¹ I think Aquinas insists that an intentio is a ratio for two reasons. First, Aquinas uses ratio in his other works in connection with divine ideas and he does so because that is Augustine terminology. So, familiarity with ratio can serve as a bridge to the Christian understanding of the term idea. Second, the term ratio gives a hint to the sort of plurality Thomas understands divine ideas to have. Since God has many rationes insofar as he understands his essence to be imitable, divine ideas are relations of imitability. And these relations are not real relations, but relations of reason, that is, relations that follow upon an act of the intellect and do not result in a real multiplicity or division. As Avicenna himself notes, relations of reason can be multiplied ad infinitum without positing any real plurality in the thing.Footnote ⁶² Thus, Thomas uses his interlocutors’ vocabulary to argue that positions they are already willing to hold (i.e., that God knows himself perfectly) entail more conclusions than they were initially willing to accept.

Second, divine simplicity and unity are paramount for Aristotle, Avicenna, and Averroes.Footnote ⁶³ Each admits divine knowledge and argues that all things have God as their source, but each does so with a great admixture of error because he wants to preserve divine simplicity. In the name of divine simplicity, they conclude either that God has no knowledge of creatures or that he only knows them in a general, imperfect, or indeterminate way.Footnote ⁶⁴ Thomas wished to correct their error concerning divine knowledge, but he had to express the correction in a way that they would accept as faithful to divine simplicity. Any solution that hinted of divine complexity would have immediately turned his opponents away. Since his interlocutors would understand the word ‘idea’ first and foremost in terms of Platonic ideas, using the term ‘idea’ would make his task more difficult. Platonic ideas are outside of God's mind, so if God required such ideas to know creatures, he would be in potency to know and, therefore, imperfect. St. Thomas chose to use the term ratio instead of ‘idea’ because he thought that ratio would be more effective at proving his point and avoided certain objections. Since he could use the terms synonymously, he chose the term with less philosophical baggage.

This apologetic explanation should be added to Geiger, Wippel, Boland, and Doolan's explanations because it makes more sense of Thomas's claim at the end of Summa Contra Gentiles I, c. 54 that a theory of divine rationes saves Plato's theory of ideas, according to which all things that exist in material things are formed.Footnote ⁶⁵ The account of divine rationes Aquinas had been articulating is similar to Plato's theory in that the rationes are certain exemplar causes in imitation of which other things come to be. The mention of the term ‘ideas’ and exemplar causality together lends credence to Wippel's explanation, but it also is a subtle way for St. Thomas to introduce his Muslim and pagan interlocutors to a Christian way of expressing the matter. Having argued that the plurality of rationes in the mind of God is required, Thomas adds this line as if to tell his interlocutors, ‘When you hear Christians speaking of divine ideas, realize that they mean nothing more than what I have said here about rationes. Plato is right that ideas are the forms according to which all things are made, but they do not exist separately from God. Divine ideas are rationes in the divine mind.’