Saturday, 17 October 2009

Q3: God's Simplicity


The second question has just shown us that we can demonstrate “that God is”. However full answers to the questions implied by “what God is” remain hidden to us; comprehension of the divine is simply beyond our intellects. This being so, it is still possible to say things about God that are true statements; especially we can say things about what God is not. Aquinas will be taking this negative (or apophatic) approach to questions about God from here until question thirteen using what is sometimes called the via remotionis (the way of remotion) or the via negativa. Questions twelve and thirteen discuss how we can know about God and what we can say about Him. They act as a transition into the next section of the summa that deals with what we can positively affirm about God, the so-called via affirmationis (the way of affirmation).

Why this Question Matters.

The Doctrine of Divine Simplicity (DDS) expresses simultaneously one of the strangest, hardest and most important facts about God; that in Him there is no composition. Its importance explains why Aquinas considers it so early on in the summa. As an analogy, in mathematics it is not uncommon to prove a highly general, abstract, theorem about which it is very hard to build an intuition; this general theorem is them applied to a number of special cases, reeling off consequences with relatively little additional effort. The DDS is rather like this; having put in the effort to demonstrate it, many consequences about God follow relatively easily. For example, later on Aquinas will use the DDS to show that since scripture tells us about relations in the Godhead (for example, Fatherhood), they must be substantial subsisting relations corresponding to the persons of the Divine Trinity.

Aquinas’s strategy in this question is to consider in turn the different ways in which there might be composition in God:

  • Is He made up of material parts?
  • Is He a composition of form and matter?
  • Is He a subject bearing a nature or essence?
  • Is He a composition of essence and existence?
  • Is He in a genus, differentiated by species?
  • Is he a composite of substance and accidents?

In each case, Aquinas shows that such a composition is impossible in God.

The Thread of the Argument

A1: Aquinas starts with the simple question of whether God is a body (in the sense of being an extended three-dimensional thing in the world). The objections, suggesting that God can be considered a body, are all based on scriptural descriptions that use bodily terminology (and are contrasted with the sed contra from John 4:24 that “God is spirit”). Aquinas offers three proofs that God cannot be a body: an unchanging first cause of change cannot be a body; God, as pure actuality has no potentiality, whereas all bodies do; and the “excellence” of a body is derived from an external principle (e.g. the soul in the case of our bodies) whereas God depends upon no external principles. Most of the objections are answered by observing that scripture sometimes uses metaphorical and figurative language when talking about God.

The second objection argues that as man is made in the image and likeness of God (Genesis 1:26) then God must be corporeal as we, His image, are. In answer to this particular biblical image, Aquinas makes a point that he will frequently repeat. It is because we are rational intellectual creatures that we are in His image, not because we are bodily creatures.

A2: Even if God is not a body, might He still be composed of form and matter? No, because in-formed matter still has potentiality; God does not. Likewise, composites of form and matter only participate in goodness (i.e. they bear the form of goodness) rather than being goodness itself like God. Thirdly, all agents (i.e. things that perform actions on other things) act as agents depending on their type of form; the first agent (i.e. God) is essentially an agent therefore must be essentially form and therefore not a form-matter composite.

The third objection suggests that God must have matter, and must therefore be composed of matter and form, because matter is what individuates things. (This dog is not that dog because it is made of a different lump of matter even though they both participate in the same form). Aquinas denies that all forms have to be received in matter. In doing so, he points out that such self-subsisting forms (like God and the angels) are individuated simply because they are not received into a subject.

A3: Aquinas next asks whether God can be considered a subject bearing an essence. (The essence of something is what makes the something what it is, and a subject is something that can receive an essence.)

The objections appeal to what seems to be common sense. For example, things in the world are not the same as their natures (a particular human is not humanity, for example). Similarly, God is the cause of creatures and causes resemble their effects, therefore God must be a subject bearing an essence.

Aquinas’s reply gives us the first major indication that he considers God as radically different from His creation: no, He is not a subject bearing an essence. Aquinas notes that for things composed of form and matter, what makes them what they are as things is not associated with their individuality but is associated with their species. Roughly speaking, form is associated with species and matter with individuation. But for things like God that are not matter-form composites, individuality cannot be derived from matter, so their forms are intrinsically individual. (Recall that we saw this argument in the reply to the third objection in the second article.) Therefore such things coincide with their natures. Aquinas immediately draws the radical corollary that God coincides with anything truly predicated of Him: He is His divinity; He is His own life and so on.

In replying to the first objection, Aquinas makes the important point that our language is adapted to talking about composite things. If we want to talk about something that is not a composite, we do so by analogy using concrete and abstract nouns to talk about different aspects of such things. This should not fool us into thinking that such linguistic differentiation implies real differentiation in the simple things themselves.

A4: Having shown that God is His own essence, Aquinas now shows that He is His own existence, thus justifying the description ipsum esse subsistens (self-subsistent existence) of God. To support his claim, Aquinas gives three arguments.

The first argument claims that if the existence of a particular thing is distinct from its essence then its existence must have a cause external to its essence. But this is a clear contradiction in the case of God as He is the first efficient cause. The second argument is similar, based on the potentiality that must be in something where essence and existence are distinct. The third argument takes a different, somewhat neo-Platonic, course. If in God, essence and existence are distinct then God can only be participating in existence. This contradicts God’s being the primary existent.

A5: Aquinas now asks whether it makes any sense to apply the notions of genus, difference and species to God. The sed contra expresses what one might anticipate given Aquinas’s treatment of God so far: the notion of genus is logically prior to the things that exemplify it, but nothing is prior to God (in any sense) therefore God cannot be allocated a genus.

Given the apparent power of such an argument, the length of Aquinas’s reply might seem surprising. But Aquinas is being careful to note that the concept of genus applies to a wider class of things than to just concrete objects in the world (for example, to mathematical objects or to privations) and he wants to make sure that all the bases are covered. He offers three arguments.

First, Aquinas claims that species arise within genii by means of the actualization of some potentiality that gave rise to the generic notion common to the genus. He gives the example of rationality arising out of the sensory, differentiating the human species from the non-rational in the genus animal. As the actualization of potentialities does not occur in God, this cannot be applied to Him.

Second, as the genus of something expresses its essence, and God’s essence is His existence, the only possible genus for God would be that of being; but Aristotle has already show that such a genus cannot exist.

Third, a genus expresses the essence of its members, but the individual members of the genus within species have their own distinct existences distinct from the genus. Therefore this cannot apply to God.

A6: As accidents realize some potentiality of their subject and as God is pure actuality, it is no surprise that God cannot be a composition of substance and accidents. Aquinas gives two other arguments about this: firstly, one cannot add anything, such as an accident, to something that is its own act of existence; secondly, as all derivation starts from God, there can be nothing derived in Him.

A7: As a sort of summing up, Aquinas states the question to which all the preceding articles have been leading: having considered all the different ways in which things can be composites, is God Himself a composite of any type or is He entirely simple?

Aquinas puts forward two objections. On the one hand, a cause will resemble its effects and all created things, caused by God, are composites of some sort; therefore God must be a composite of some sort. (This generalizes the argument of the second objection to the third article above.) On the other hand, in the world of which we are aware composite things are better than simple things, therefore we should not attribute simplicity to the best of all possible things. For the moment however, Aquinas leaves the answers to these objections until later in the summa (Ia.q50.a2 ad 3 and Ia.q4.a2 ad 1 respectively).

In his response to the question, Aquinas summarizes the articles that have gone before showing that God is not a composite in the ways considered. He also adds some additional observations: a composite is subsequent to its components, but God is not subsequent to anything; the composition of any composite is caused, but God is the uncaused first cause; in any composite there must be a mixture of potentiality and actuality, but God is pure actuality; and finally, within a composite there are things that are not the composite itself, but God is pure form in which this cannot be the case.

A8: Finally, having disposed of the notion that God is a composite considered in Himself, Aquinas considers the possibility that He might enter into composition with other things. Aquinas’s major concern in this question seems to be to refute three major errors: that God is the soul of the world; that God is the form of all things; or that God is prime matter. Each of these involves God being a component of some sort of composite.

Aquinas’s response (although it could just reiterate what he has said already) appears to be tailored to the motivations behind the erroneous propositions. So he argues that a first efficient cause may resemble its effects but need not be numerically equal to them; components cannot be primarily and essentially efficient causes in the way that God is; and a part of a composite cannot be the first being, as form, when part of a composite, participates in that something rather than being that something essentially.

Handy Concepts

  • Everything is either pure actuality (i.e. God) or a mixture of actuality and potentiality.
  • God is not a body made up of parts because such a composite would retain un-actualized potentiality.
  • God is not a composite of form and matter.
  • Something participates in a form when if it bears the form but is not identical with it.
  • The second argument in the second article is going to have profound implications when generalized later on. Aquinas differentiates between being a such-and-such by participation (I am a human being because I bear the form of a human being) and being a such-and-such by essence (God is good by His very nature). When this distinction is applied to the notion of being itself, we arrive at the idea of God as ipsum esse subsistens (self-subsisting being) as in the fourth article.
  • The essence or nature of a thing is what makes that thing the sort of thing that it is. A subject is what receives or bears an essence. God is not a subject bearing an essence.
  • God coincides with anything truly predicated of Him.
  • God is self-subsisting existence (ipsum esse subsistens).
  • God is prior to any notion of genus and therefore is not in any genus, let alone differentiated as to species.
  • A substance is a concrete particular thing that bears attributes. Accidents are attributes of things that are not essential to their identity. God is not a composition of substance and accidents.
  • God is not a composite in any sense, nor does He enter into composition with other things.
  • Davies, in Thomas Aquinas on Good and Evil, helpfully sums up the notion of the simplicity of God as affirming that God is (i) not changeable, (ii) not an individual belonging to a natural kind, and (iii) not created.
  • The doctrine of God’s divine simplicity is not original to Aquinas; indeed it was taught as a doctrine of the faith by the fourth Lateran Council before Aquinas was born.


  • Why is it that God’s simplicity is the hardest thing to write about?
  • In the third article, Aquinas makes the claim that effects resemble their causes. This is a claim that will be repeated many times throughout the summa; especially in the form omne agens agat sibi simile (every agent makes its like). This may seem rather odd, but what Aquinas means by this is that an agent cause expresses something of its own nature in the effect that it has on a patient as it is actually having the effect. So a vat of acid doesn’t look like a dissolving piece of metal but as the acid is at work dissolving the metal it expresses something about itself in the very act of dissolving. This should remind us that Aquinas thinks of causes in very immediate terms: he’s not just interested in the fact that a virus causes a cold; he’s interested in the way in which the virus acts in causing the cold.
  • The idea that created things are composites of essence and existence is a controversial issue at the foundations of metaphysics. Aquinas nailed his colours to the mast very early in his career with the work de esse et essentia.

Revised March 2012

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