Thursday, 31 December 2009

Question 5: The General Notion of Good

Why this Question Matters.

In Ia.q4 Aquinas considered the idea of perfection, which he noted has a relation to the good. In this question, he is going to inquire into the nature of goodness itself. Completing the sequence with the next question, Ia.q6, Aquinas is then going to enquire into the relationship between God and the good.

The important principle that Aquinas establishes in this question is that there is a fundamental relationship between good and being: They are two aspects of reality that lie outside Aristotle’s categories (thus they are transcendentals) that present to us different aspects of the same reality; they are what is called convertible. Absolutely basic to Aquinas’s approach to metaphysics is the foundational aspect of being. Although good and being are convertible, being is the more fundamental idea. As we already know that there is a fundamental relationship between God and being we are thus prepared for the idea that God and the good are intimately related.

The Thread of the Argument

A1: Aquinas launches straight into the main thread of this question: that good and being are the same in reality (i.e. they are convertible as transcendentals) and that we can only differentiate between them conceptually. The main objection to this point of view seems quite reasonable and even to hold the balance of probability: we use the terms good and being in different ways, so they must be different in reality.

Aquinas’s strategy is to admit that they are conceptually different, but that they are different concepts of the same underlying reality. He adopts Aristotle’s definition of the good: things in the world have an innate tendency towards their own perfection (from which, of course, they may be obstructed) and their perfection consists in the actualization of their potentiality. But Aquinas has already argued (in Ia.q3 & Ia.q4) that things actualize their potentiality to the extent that they exist: perfection consists in their fullness of being. Since the good is precisely this actualization of potentiality, good and being are fundamentally the same reality.

Aquinas gives an extended answer to the first objection concerning the different ways in which we use the terms good and being. If we picture a thing as coming into existence and then over the course of its existence as moving towards its ultimate perfection, then we say that at the point it comes into existence it exists “without qualification” but that it is good only in a “qualified way” (it has not achieved its ultimate good). However, if it achieves its perfection then it is good in an unqualified sense but that since its existence is more than just a bare existence, it exist in a qualified way (i.e. its initial existence has had all perfections added to it).

A2: Having established their relationship, Aquinas asks whether one of good or being can be considered more fundamental than the other. He answers that it is being that is the more fundamental; but he continues by addressing some quite reasonable objections. These objections are founded on the facts that we are far more used to the idea that good has a wider range of meanings; that there is a wide range of shades of these meanings; and these meanings can be applied to more than just beings that currently exist.

Borrowing an idea from Aristotle’s Metaphysics, that “in order to be known, a thing must actually be”, Aquinas argues that a thing’s existence is prior to anything that we can know or say about it. Being is the most fundamental intellectual idea and is the proper object of the intellect.

In answering the objections, Aquinas observes that we are often interested in things from the point of view of causality. It is this that gives rise to the idea of good being prior to being. In causality, the end (i.e. a thing’s ultimate good, the “cause of causes”) gives order to all the efficient causes that are directed toward that end; therefore we tend to think of that good as prior to the being that is moving from potentiality to actuality. Aquinas insists that this is not thinking fundamentally enough; being is prior to the good for the reasons he gives in his answer.

A3: Having demonstrated the convertibility of being and the good, Aquinas must now address the obvious question of how we can bring ourselves to call good things that are either conspicuously evil or for which goodness seems a strange description. Aquinas builds on the classic scriptural answer that “all of God’s creatures are good” (1 Tim 4:4). Everything other than God is created by God and is good insofar as it has being; for we have already seen in the first article that good and being are really the same underlying reality. Evil, on the other hand, does not have its own existence. It is a privation, something missing, a failure of actualization of potentiality in something that does exist.

Some things for which “good” seems an odd description, like prime matter or the objects of mathematics, do need careful consideration. Prime matter doesn’t exist in itself (it has to be in-formed), so we should call it potentially good; the objects of mathematics don’t exist in the same sense as concrete objects but only conceptually, so we can think of these things without reference to good.

A4: Having touched on the relationship between good and causation in the second article, Aquinas now returns to give a more thorough treatment. The objections observe that we can talk about the good or about goodness in the context of formal or efficient causation; but Aquinas insists that good is most properly associated with final causation. His answer is basically a reiteration and amplification of what has gone before: from the definition of the good, it is clear that it provides a final cause and such final causes are conceptually prior to the other causes, providing their motivation and ordering.

He makes the important observation that although a final cause orders the other causes, when we observe a caused thing we start with the observation of its form and work backwards inferring its final cause.

A5: Next, Aquinas asks whether goodness is to do with mode, species and order, a question derived from the thought of St. Augustine. The idea of the mode of something’s being is to do with how well that something expresses its form. Augustine relates mode to measure; so, for example, I might say that my mode of being does not express my form too well if I am too fat or lazy. Aquinas seems to take the notion more generally than Augustine but it is still clear that the notion is related to the good of something inasmuch as a poor mode of being reflects a failure to actualize potentiality. Similarly, the species of something is determined by its substantial form, which tells us what sort of a thing it is. Something is good if it is in accord to its substantial form (and accidental forms associated with it are not “obstructing” its substantial form). Finally, things gravitate toward what is natural for them; so if they are correctly ordered, their being is in accord with what their being should be. The objections in this article are dealt with by clarifying the difference in meaning between mode, species and order considered as goods and the good itself.

A6: Having considered St. Augustine’s division of the good in the fifth article, now it’s the turn of St. Ambrose, who divided the good according to the worthy, the useful and the delightful. Aquinas observes that we might think of the motion of a thing from potentiality to actuality in analogy to the usual idea of physical motion. In physical motion from a starting point to a terminal point the thing in motion goes through intermediate points. These intermediate points might be thought of as useful in the journey towards the terminus. The terminus itself may be thought of from two points of view: the final goal itself, which may be thought of as worthy; and the fact of resting in that final goal, which might be thought of as delightful.

Summary and Handy Concepts

  • In this question Aquinas quotes Aristotle saying that “the good is what all things desire”. The sense of the word “desire” corresponds to seeking. Modern translations of the Nicomachean Ethics (directly from the Greek, rather than indirectly via the Latin that was available to Aquinas) usually read “the good is that which all things seek”. This latter is certainly the sense that Aquinas uses. Even more, the sense is that of “have an innate tendency towards”; this tendency is not restricted to creatures capable of desire in the sense that we usually use it.
  • Good and being are transcendental aspects of the same reality, differentiated only conceptually. However, being is the more fundamental concept than the good because “in order to be known, a thing must actually be”.
  • We may connect what Aquinas says in his reply to the first objection of the first article to the distinction between predicative and attributive adjectives made by Peter Geach in considering the good. If we think of a sentence like “this is a red ball” then we will have no qualms in thinking this equivalent in meaning to the pair of sentences “this is red” and “this is a ball”. However, if we consider the sentence “this is a big mouse” we can see that this is not equivalent to the pair of sentences “this is big” and “this is a mouse”. In the first case “red” is a predicative adjective; in the second case, “big” is an attributive adjective. Understanding the latter demands the context within which it is used. In general, Aquinas understands “good” as an attributive adjective; we need to know what aspect of goodness is being talked about. To say that “she is a good chef” is to talk of the perfection of that person as a chef. If we were simply to say “she is good”, then we would have to be talking about Aquinas’s unqualified sense of goodness; we would be attributing to her the achievement of her ultimate end as a human being (presumably in the beatific vision).
  • Evil does not have its own being; rather, it is a privation of the good.
  • Good is most properly associated with final causation.
  • Mode, species and order are aspects of goodness associated with the ways in which a thing may actualize its potentiality and therefore be good.
  • The good may be thought of in terms of the worthy, the useful and the delightful by considering the movement from potentiality to actuality analogically to ordinary local motion.


  • Much of the explanatory meat of the first question is contained in the answer to the first objection. This shows that one has to be careful not to simply trim the summa down to Aquinas’s main responses.
  • It’s interesting to speculate what Aquinas would have made of Descartes’s cogito argument against the radical doubt of self-existence. For Aquinas, being is the very first object of the intellect and therefore he might have considered Descartes’s argument simply to beg the question. We cannot even get started with intellectual inquiry if we do not admit the being of the subject performing the inquiry.
  • Aquinas’s approach to things like mathematical objects and the good looks slightly ad hoc.
  • In the fifth and sixth articles Aquinas’s attempts to marry his notion of the good with the divisions of the good put forward by St. Augustine and St. Ambrose seem a little forced.

Revised 20/03/12

Question 4 - God's Perfection

Why this Question Matters.

Matthew 5:48 tells us to “Be perfect, as your heavenly Father is perfect”. This is always something of a puzzle for those that hear this teaching, as we are so aware of our imperfections before God. Later on in the summa, Aquinas is going to enquire into what it means for us to be perfect and into how the life of grace forms us in such perfection. But first of all, he is going to ask about what perfection is in general and in particular what it means when we ascribe perfection to God. Aquinas will conclude that the notion is to do with how God is the first efficient cause of every created thing; since effects resemble their causes, it is natural at this point for him to also inquire into it means for a creature to resemble God.

In the preamble to this question Aquinas notes that there is a relationship between the idea of perfection and the idea of the good. As he is going to discuss the latter in the next question, it makes sense to see these two questions as a doublet.

The Thread of the Argument

A1: If we look at the etymology of the word “perfect” we see that it carries meanings like “thoroughly made” or “completed”. Since God is not in any sense made, then surely we should not apply the idea of perfection to God. Similarly, if we consider God to be the origin of all things and we observe that origins tend to be less perfect than the completed beings to which they are directed (an acorn being less perfect than an oak tree, for example), then it is hard to attribute perfection to God.

Aquinas answers by making a distinction between meanings of the word “origin”. One should observe that God is the origin of a thing in the sense that He is the first efficient cause of that thing, sitting as the foundation of the chain of causes bringing it from potentiality to actuality. This is in contrast to the notion of origin, exemplified by the acorn, which refers to something material which is in potentiality to become the actuality of the completed thing.

Everything created is a composition of actuality and potentiality and God is the first efficient cause of the movement of such beings from potentiality to actuality. Since the first efficient cause of everything has to be the most actual thing possible, it is reasonable to identify this thing as the most perfect of all things. Indeed, we can go on to extend this notion of perfection by analogy from God to creatures by saying that something is perfect when it has achieved actuality in all that makes it what it is.

Returning to address the objections, we must admit that in ordinary use the word “perfect” does refer to things that are made. But if we are to have a vocabulary that refers to God, we must be able to extend ordinary meanings into the sphere of the transcendental. Indeed, we might even consider that the notions and meanings we apply to created things themselves are better derived from analogies that we make between God and created things. Likewise, if we think about material origins, like the acorn as the origin of an oak tree, we have to remember that the acorn has an origin too! Anything that is in potentiality must have derived its being from something in actuality, and only something actual can actualize something that exists in potentiality. God lies behind all this as the first efficient cause.

A2: God is not only perfect, but His perfection contains the perfections of everything else. Aquinas argues for this point of view by observing that since God is the first efficient cause of created things, and since causes contain their effects, therefore God must contain the perfections of all created things in the highest manner possible.

We saw in Ia.q3.a3 that effects resemble their causes in that something of the nature of a cause must be expressed in the effect that the cause has. If we think about efficient causes, then we can say more: the perfection found in an effect must derive from the cause. After all, it is the efficient cause that moves the thing from potentiality to actuality and is therefore the source of the perfection of the thing. What is more, we can identify this happening both when the efficient cause is the same sort of thing as the effect (i.e. when the cause generates the effect formally) and when they differ (i.e. when the cause generates the effect eminently).

Aquinas goes on to offer a second argument in favour of this position by observing that God is a self-subsistent being, containing the full perfection of existence. Since the movement of potentiality to actuality involves the coming to be of that actuality, created things are perfect inasmuch as they exist in some way. God, being the efficient cause of that being, must contain that being most perfectly within Himself.

A3: There is a profound distance between God and His creatures, but it is reasonable for us to ask how a creature might be considered to resemble God. After all, we are the effects of God’s causality and effects resemble causes. We also have the backing of scripture (Genesis 1:26 & 1 John 3:2) that tells us that we are like Him in some way.

Aquinas answers by observing that similarity is founded in some sort of sharing of form. Therefore to answer the question of the similarity of creatures to God, we must first look into the different ways in which forms may be shared. Then we may identify if any of these ways of sharing form can be applied to the case of creatures sharing form with God. Aquinas rejects a couple of cases of sharing a form, (for which he gives examples of things being identically white and not-identically white), before he settles on the answer that he considers adequate for this question. When two things share a genus or, even more closely, share a species, there will be a closeness of resemblance between them that corresponds to this sharing of genus or species. For the case of God, outside of any genus, the similarity has to be far more remote. What God and creatures do share is being. Now, God is being by His very essence and creatures participate in being in receiving their being from Him. It is in this way that creatures can be considered to resemble God, by participation in the being that He is by essence.

The third objection argued that there can be no resemblance between God and creatures on the grounds that resemblance is founded upon similarity of form and there can be no similarity of form between creatures and that whose essence is to exist. In answering this objection, Aquinas makes the fundamental point that, once we have identified what it means for a creature to resemble God, we have to recognize that there is a profound asymmetry in the resemblance between God and creatures. Creatures can be considered to resemble God, but God cannot be said to resemble creatures.

Handy Concepts

  • God is the most perfect being in the sense of being the first efficient cause of the being of all things and therefore the most actual of all things. Perfection in creatures may be thought of as actualized potentiality; similarly, it may be thought of as fullness of their being.
  • God, because He is the first efficient cause of all created things, contains all the perfections of all these things within Himself.
  • As effects resemble causes, so God’s creatures resemble Him. But this is a remote resemblance founded on the fact that creatures participate in the being of God. There is a profound asymmetry in the resemblance: creatures resemble God in this way, but God does not resemble creatures.


  • At this stage, Aquinas’ notion of our similarity to God may seem not to do justice to the scriptural account. However, Aquinas will develop this account over the next few questions, so it is important to not leap to conclusions quite yet. Questions Ia.q12 and Ia.q13 will be very important in this regard.
  • In this question we get strong hints of Aquinas’s doctrine of the Analogy of Being. Creatures receive their being from God and participate in that being, but as the being of the creature is not identical with being, this being is analogical to God’s being. For more details on the analogy of being, please refer to the bibliography. For a modern, short, but quite sophisticated treatment of the subject, take a look at Steven Long’s book Analogia Entis.

Revised 18/03/2101

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

Q2: The Existence of God

Why this Question Matters.

Having established the nature and scope of sacred teaching in the first question, Aquinas turns to the question of the existence of God. It is important to note that here and in the next few questions, he is concerned with the existence and nature of God as known to natural reason (following St Paul in Romans 1:19-20). How God is known from revelation and the relationship between natural and revealed knowledge of God will follow later. The third article of this question lays out the famous quinque viae (five ways); these are five arguments from natural reason to prove the existence of God.

The Thread of the Argument

A1: Aquinas asks first whether the existence of God is self-evident. Three objections in turn suggest the following: that knowledge of God is implanted in us by God and is therefore self evident; that God being “that than which nothing greater can be conceived”, He must exist, as to exist is greater than not to exist. (This is the so-called ontological argument of St. Anselm.); and that God being truth itself (John 14.6), His self-evident existence follows from the self-evident existence of truth.

In answer, Aquinas makes a distinction between propositions that are self-evident in themselves but which are not known to us because we do not know what the terms of the proposition really mean, and propositions which are self-evident in themselves and known to us because we do. As we do not really know what God is, the proposition that God exists is placed in the former category. In Ia.q3.a4, Aquinas will demonstrate that God is His own existence, therefore the subject and predicate in the proposition “God exists” are identical; therefore the proposition is self-evident in itself. However, the proposition is not self-evident to us and has to be demonstrated by sophisticated arguments based on those of God’s effects that are known to us. This latter Aquinas will outline in the third article.

The failure of the first and third objections is now clear by means of the distinction. The ontological argument is rejected on the two grounds that it is unclear that the characterisation of God is correct and that also that the reasoning is faulty. Aquinas demands that for the argument to work we must in fact know that “that than which greater can be thought” must exist; which rather ruins the argument.

A2: Before actually presenting arguments for God’s existence, Aquinas asks the more fundamental question of whether it makes any sense to try to demonstrate God’s existence. The objections suggest that the existence of God is an article of faith and that it makes no sense to demonstrate matters of faith; that we don’t know what God is and therefore we can’t demonstrate God’s existence; and that as all we could naturally know of God arises from his finite effects (i.e. those known to us) we could not know about the infinite God.

Aquinas replies that there are two types of demonstration: from cause to effect and from effect to cause. The first type of demonstration answers questions of the form “why is something the case”; demonstrations of the second sort answer questions of the form “that something is the case”. Demonstrations of God’s existence are of the second type (Romans 1:20): they can tell us that there is some cause causing an effect even if we can’t infer much about the cause itself. The second and third objections fall immediately. To the first objection Aquinas points out that faith presupposes natural knowledge, so a natural demonstration of God’s existence (which faith reiterates, or upon which faith may build) is reasonable.

A3: After having argued that, in principle, one can in fact construct demonstrations for the existence of God, Aquinas proceeds to do so. He presents the famous quinque viae (five ways).

Before he gets under way two objections are presented which are objections to the very existence of God. The first is a version of the argument from the existence of evil; God must surely be infinite Good and if He exists then evil could not. The second uses what later became known as Ockham’s Razor; we can explain the world in terms of natural causes therefore there is no reason to posit the existence God. The first objection is countered with the observation that God can permit an evil so as a good may come from it; the second is rejected because Aquinas denies that we do get a full explanation of creation from within itself.

The first of the five ways argues that anything changing is being changed: its potentiality is being actualized by something external to itself. But that something is itself being moved from potentiality to actuality by something external; and so on. However, the chain of agents cannot be infinite, therefore there is a first agent that cannot itself be being moved from potentiality to actuality, therefore it is pure actuality and we call it God.

The second of the five ways is similar in form to that of the first way but applies the reasoning to “per se” series of efficient causes to infer that there must be a first efficient cause.

The third way observes that if there was ever a point at which absolutely nothing existed, then nothing could ever exist, because things depend on other things for their coming to be. Aquinas goes on to infer from this that there must be some thing, the existence of which is necessary (rather than contingent). Another infinite regress argument (this time on necessary things receiving their necessity from other necessary things) arrives at a first necessary thing which we call God.

The fourth way argues that the existence of different grades of perfection (with respect to various properties) in created things points to a most perfect thing with respect to such properties, which we call God.

Finally the fifth way observes that non-intellectual things act for an end, from which Aquinas infers that some intelligence, which we call God, must be supplying that end to them.

Summary and Handy Concepts

  • Something may be self-evident in itself, in the sense that the predicate is implied by the subject’s definition, but not known to us because we don’t have a true understanding of the terms that express that thing. The proposition “God exists” is a proposition of this sort.
  • Demonstrating why something is the case (from cause to effect) and demonstrating that something is the case (from effect to cause) provide two different approaches to the notion of demonstration. Demonstrations of the existence of God based on natural reason are demonstrations of the second type.
  • Aquinas believes that our only natural access to God is through our sensory experience.
  • The division of being into actuality and potentiality, with God the only being that is pure actuality, is absolutely fundamental in Aquinas’s thinking about God. He will use this idea throughout the summa and especially in the questions about God. In recognition of this, the very first of the twenty-four Thomistic theses approved by the Sacred Congregation for Studies in 1916 is dedicated to this division of being.
  • For more details of the metaphysical assumptions underlying the five ways, please refer to the section on Metaphysics.


  • Given the enormous attention paid to the ontological argument over the ages, Aquinas is really quite dismissive of it. This reaction may very well arise from Aquinas’s belief that we can only naturally approach God through created causes. This approach means that even framing the concept of “God” in the way that St Anselm frames it needs some preparatory work; how do we know that St Anselm’s definition is coherent, for example?
  • The objection to the existence of God based on the existence of evil is also despatched very quickly. For those wanting in depth treatments of the so-called “problem of evil”, two books by Brian Davies are highly to be recommended: The Reality of God and the Problem of Evil and Thomas Aquinas on God and Evil.
  • It’s clear that the five ways were well known to the audience of the summa, as the treatment is very brief. The brevity of our summary above reflects the brevity of the arguments as presented by Aquinas! But Aquinas takes a lot of metaphysical assumptions for granted that we have to recover from other sources and an adequate treatment of any of the five ways takes many pages of careful argument. One of the best and most accessible modern accounts of the five ways is given in Edward Feser’s book Aquinas. Aquinas himself goes into much more detail about natural theology in the summa contra gentiles.
  • The reader must be warned that there are many terrible accounts of the five ways out there. The common feature of many of these is to attempt to interpret the terms used in the arguments as they tend to be used in modern philosophy (or indeed, without any recourse to philosophy at all). For example, the modern notion of a cause is radically different from that assumed by Aquinas.
  • In the third way, Aquinas infers the existence of (at least one) necessary being by an argument that, on a first reading, appears to commit what is called a quantifier shift fallacy. He appears to argue that because for each thing there is a time when it must not be, therefore there is a time when all things must not be, which is clearly fallacious. Here, perhaps, is one of those rare occasions where an argument ad hominem is justified: Aquinas simply would not have made such an elementary slip, so another explanation must be found. Perhaps, as Freddoso argues, Aquinas might be read as hypothesising that if everything is subject to generation and corruption then there must have been a time when there was nothing, as everything includes the prime matter out of which material things are made. For another argument, refer to Feser op. cit.
  • The fourth way, from the grades of perfection in creation, is generally held to be the weirdest for modern people to get their heads around. Indeed, it is possible to look at what Aquinas has written and to ask where the argument is. Again, the account that Aquinas gives does not really do justice to the subtlety of the argument.
  • Similarly, Aquinas’s account of the fifth way is disappointingly short especially as this may very well be the most profound of the five ways.

Revised March 2012

Introductory Books

"Of making many books there is no end, and much study is a weariness of the flesh" (Eccl 12:12)

There are many books about Aquinas, about his thought and about his intellectual and spiritual impact throughout history. Here are some suggestions for books that I have found very helpful for covering the basics of Aquinas's thought in clear language.

  • Edward Feser, "Aquinas: A Beginner's Guide", OneWorld, ISBN 1-8516-8690-8

This has now become my first recommendation for a book introducing Aquinas’s thought. Although this is entitled a "beginner's guide", it does assume slightly more background in the history of philosophy than the two books by Brian Davies that we mention below. Making this assumption allows Feser to connect Aquinas's thought with other philosophers (especially of the early modern and contemporary periods). From this book, you'll get a good idea of how the great tradition of metaphysics was rejected (without all that much in the way of rigorous refutation) in the early modern period and how it is making something of a comeback today.

  • Brian Davies, "Aquinas", Continuum, ISBN 0-8264-7095-5
  • Brian Davies, "The Thought of Thomas Aquinas", Clarendon Press, ISBN 0-1982-6753-3

Brian Davies is an English Dominican who is currently professor of philosophy at Fordham University in the USA. There's a lot of overlap between these books, but both of them are excellent and if you like one, it's worth getting the other! Davies will give you more background than Feser, but he also approaches Aquinas as a discussion partner from the point of view of modern analytic philosophy in the Anglo-American tradition. You may find this a strength or a weakness!

  • Fergus Kerr, "Thomas Aquinas: A Very Short Introduction", Oxford University Press.

I have to admit that I haven’t read this book, but anything written by Fergus Kerr is worth reading! In my experience, the OUP "Short Introductions" tend to be pretty useful. And it's cheap!

  • GK Chesterton, "St. Thomas Aquinas" (many editions).

A classic, with the style that only GK could muster! Still worth reading today.

We've given links to a couple of online translations of the summa. In the sessions we're generally using the Freddoso translation backed up with the English Dominican translations. It's also worth mentioning:

  • Brian Davies and Brian Leftow (eds.), "Summa Theologiae, Questions on God", Cambridge University Press.

This gives a good modern translation of Questions 1-26 (omitting questions 16, 17, 23 and 24), improving (in our opinion) on the corresponding volumes of the later English Dominican translation.

  • Timothy McDermott (ed.), "Summa Theologiae, A Concise Translation", Christian Classics.
This compresses the most important bits of the summa into a single volume. The ambition of this book is extraordinary and I think it’s a tribute to the author to say that he often succeeds in distilling the essence of the summa. However, I’ve found some of the choices for inclusion and omission to be slightly frustrating and the translation a little bit loose in places. Definitely worth having to hand, but the reader should be prepared to dive into the full text in places.

Another translation worth mentioning is that published by the Aquinas Institute ( This provides an update to the earlier Dominican Translation, and is published as a parallel Latin/English text.

NB: Edward Feser has also published a robust philosophical refutation of the ideas of the "new atheists" in his volume "The Last Superstition" (ISBN 1-5873-1451-7). One might note that the tone of this book is quite "bare knuckle" - not attempting to spare the feelings of his opponents. It is, however, the most accurate and accessible refutation of those opponents that I know of and a fine introduction to the metaphysical and theological thought of Aquinas.

Tuesday, 22 September 2009

Question 1 - What is Theology

Why this Question Matters.

Aquinas poses some basic questions about what sacra doctrina (sacred teaching) is. In a sense, this first question is fundamental to the rest of the work because in it Aquinas provides a justification for rational enquiry into sacred teaching. Sacred teaching is not simply a matter of passive reception of revelatory knowledge but involves all the intellectual faculties of the rational animal, man.

The Thread of the Argument

A1: In the first article Aquinas points out that although philosophical reasoning is sufficient for us to demonstrate the existence of God and to describe to a limited extent what He is like, sacred teaching (through revelation) goes beyond what natural reason can reach. In particular, sacred teaching makes known to us the supernatural end to which we are ordered; we have to know about the end towards which we should strive if we are, in fact, to strive towards it. In addition, philosophical investigations about God are very hard, open to very few, and are prone to error. Divine revelation ensures that the mistakes that our fallible natural reason will make about God are corrected. Our salvation depends upon us knowing the truth about Him.

In the second objection, Aquinas introduces us to two of the transcendentals. These are aspects of being that lie above the ten categories of Aristotle. Here he claims that truth and being are convertible. By this he means that whatever is true is something that exists and whatever exists is something that is true.

A2: Aquinas now enquires as to whether sacred teaching is a science, in the sense of being a body of knowledge deduced from assumed first principles. In answering the question, Aquinas makes a distinction between sciences whose first principles are self evident in themselves (such as arithmetic or geometry) and those in which the first principles are known from a higher science (such as optics or music). He concludes that sacred teaching is a science of the latter sort, depending on first principles revealed by God.

A3: Sacred teaching appears to deal with many different kinds of things: for example, God, human beings, human behaviour, animals and angels. Can it then be considered as a single science as, according to Aristotle, each individual science deals with one kind of subject? Aquinas insists that sacred teaching is a single science (as opposed to a collection of different sciences) as all the topics it deals with can be described under the single heading of “those things divinely revealed”.

A4: Aristotle divided the sciences into the theoretical, the poetical and the practical. Aquinas asks whether sacred teaching is practical (i.e. ordered to guiding human practice, like politics or ethics) or theoretical (i.e. ordered to understanding rather than action, like mathematics or physics). The objections point out that much of sacred teaching is precisely ordered towards what we should do, and therefore we should consider it as a practical science. However, Aquinas argues that it is in fact both practical and theoretical, but that it is more theoretical than practical. This is because it is primarily ordered to divine things and only secondarily to what people do as a consequence of the knowledge of divine things.

A5: Aquinas now argues that sacred teaching is the most “noble” of the sciences. At first sight, this position might appear to be difficult to argue for: the first principles of other sciences look to be on much firmer ground. Also one might argue that a science that has self-evident principles is higher than one that derives its first principles from elsewhere.

But Aquinas argues that, from the point of view of being a theoretical science, the conclusions of sacred teaching are more certain than those of other sciences. After all, God’s revelation is more certain than the conclusions that fallible human reason can reach in the other sciences. It is this criterion of certainty by which we should judge the nobility of theoretical sciences. We should also remember that its subject matter is beyond what is reachable by unaided human reason.

From the point of view of a practical science, sacred doctrine is ordered towards the eternal happiness of human beings. This is the end to which the ends of all other sciences are ordered and on this ground it therefore it surpasses all human sciences.

A6: Can sacred teaching be considered as wisdom? Aquinas considers the wise man to be the one who regulates and judges, where judgement is made on the basis of lesser things considered in the light of higher causes. For example, the architect has a higher wisdom than the artisan who puts the bricks one on top of another. In the light of this definition of wisdom it is easy to see that, since God is the highest cause in the universe, one who has knowledge taught by God is wise. Indeed, we must say that sacred teaching is wisdom to the highest possible degree.

A7: Aquinas now asks the rather curious question “Is God the subject of this science?” The question is motivated by the two objections: if we can’t define the subject (God), how can we say that He is the subject; and since sacred teaching covers many subjects, how can we identify a single subject. Aquinas answers by pointing out that it is obvious that everything in sacred teaching flows from considerations of God. To the objections he responds that although we cannot know God, we can infer enough knowledge of Him from his effects for Him to be the subject of sacred teaching. In addition, although there is much diversity in the subjects of sacred teaching, they are all traced back to God.

A8: The eighth article considers the perennial question of the place of reason in sacred teaching by asking what role argumentation has, if any. Against the use of argument in sacred teaching statements of an Apostle and three of the Fathers of the Church are presented as evidence for the prosecution: faith displaces all need for argument; the written scriptures contain all that is needed; there may be arguments from authority rather than from reason, but they are weak arguments indeed and unworthy of such a noble subject.

Aquinas’s strategy is to differentiate between the first principles of sacred teaching which are infallibly received from scripture, and the articles of faith which can be deduced by rational argument from them. Thus the first objection quickly falls as reason has its place in sacred doctrine in the process of the deduction of the articles of faith from the divinely revealed first principles. Of course, if someone does not believe what has been divinely revealed, there is no possibility of proving the articles of faith to them. However, as the first principles have been divinely revealed and are therefore true, it is impossible for a rational argument to refute the articles of faith.

In a lengthy rebuttal of the second objection, Aquinas makes the distinction that arguments based on human authority are weak but that if the authority is divine, the argument is strong. He also argues that reason helps to clarify revelation: “As grace does not abolish nature but brings it to perfection, natural reason should assist faith as the natural inclination of the will yields to charity”.

A9: Should sacred teaching use metaphorical or figurative language? It would appear not as the idea of a science is to clarify the truth rather than to make it more obscure. But on the other hand sacred scripture itself clearly uses such language at times. Aquinas points out that the subject of sacred doctrine is beyond our comprehension and therefore it is perfectly appropriate that scripture describes divine things by analogy to created things. If scripture can do it, so can sacred teaching. The reply to the second objection gives the additional reasons: figurative language can serve to hide things from those who seek the truth as a challenge; and from those unbelievers ready to ridicule the faith.

A10: Finally in this question, Aquinas turns to the meanings of scripture: can one passage of scripture bear more than one meaning? Here Aquinas describes and defends the medieval doctrine of the four ways of interpreting scripture. To do this, he observes that words can signify things; this signification gives us the literal (or historical) sense of scripture. But the things signified by the words can themselves signify further realities; this further signification leads to the spiritual senses of scripture. These spiritual senses are divided into three: first there is the allegorical sense in which concrete things point to what is to be believed (for example, much of the Old Testament points allegorically towards Christ); the tropological (or moral) sense of scripture which points to the things that we should and shouldn’t do; and the anagogical sense of scripture which points towards our eternal glory.

A medieval poem summarizes these meanings as follows:

littera gesta docet,
quod credas allegoria,
moralia quod agas,
quo tendas anagogia.

The letter teaches deeds,
Allegory teaches what you should believe,
Morality teaches what you should do, and
Anagogy teaches where you should set your aim.

Aquinas is quite clear that the spiritual senses presuppose the literal sense and are based on it; therefore the spiritual senses cannot “override” the literal sense.

The reply to the third objection makes clear that parables are included in the literal sense of scripture. Words taken literally can signify either strictly or figuratively; when they signify figuratively, the literal sense is not the figure but the meaning of the figure.

Summary and Handy Concepts

  • Philosophical reasoning can get us so far in understanding God, but not far enough. Revelation is required to reveal to us the true supernatural end of human beings as well as to aid and correct us in our philosophical investigations about Him.
  • The trancendentals “truth” and “being” are convertible. Aquinas will return to the convertibility of all the transcendentals elsewhere in the summa.
  • Sciences can be divided into those that have self-evident first principles and those whose first principles are revealed by a higher science. Sacred teaching is a science in this second sense.
  • Sacred teaching can be considered a single science (in the sense of Aristotle) because its subject is unified as being all things revealed to us by God.
  • Sciences are divided into the practical (ordered towards action) and the theoretical (ordered towards understanding) and the poetical (which Aquinas does not cover in this question). Sacred teaching can be considered both practical and theoretical but more theoretical than practical as it is ordered towards divine things.
  • Both as a theoretical and as a practical science, sacred teaching is the noblest of the sciences. For the former its conclusions are the most certain of the sciences as it is taught by God; for the latter it is ordered towards the ultimate end of human beings and as such provides the ends for all other practical sciences.
  • Sacred teaching is wisdom because it is ordered to the highest cause in the universe.
  • God is the subject of the science of sacred teaching because although the subject covers many topics, they are all ordered toward God.
  • The place of rational argument in sacred teaching lies in the deduction of the articles of faith from the divinely revealed first principles of the science. Although argument from authority is usually considered a weak argument, argument from the authority of scripture is strong because of the one who reveals it.
  • Scripture can use metaphorical or figurative language. God is so far beyond our comprehension that it is quite appropriate that his message is conveyed via material metaphors or via figures.
  • Scripture can bear four senses, the literal and the three spiritual senses. It is important to note that such things as parables should be considered under the literal sense; the words used signify not the figure but what the figure means.
  • For a modern consideration of many of the issues that are discussed in this first question, you may wish to consult the encyclical Fides et ratio of Pope John-Paul II.


  • The question of what Aquinas means by sacra doctrina, and how it should be translated into English is a well-known subject of argument. I’ve translated it as “sacred teaching” and have interpreted the science of sacra doctrina as that which is revealed (the first principles) and what can be rationally inferred from it. The following papers may provide some illumination about the issues involved. Davies - Is Sacra Doctrina Theology? - New Blackfriars 71 (1990); Weisheipl - The Meaning of Sacra Doctrina - Thomist 38 (1974); and O'Brien – Sacra Doctrina Revisited: the Context of Medieval Education - Thomist 41 (1977).
  • As Aquinas goes on to talk about natural theology for the next twenty or so questions, one might infer that he includes or at least presupposes it in sacra doctrina.
  • Article 5 claims a certainty for sacred teaching beyond that obtainable in the human sciences. But in sacred teaching we use fallible human reasoning, so it would seem to suffer similar problems. Perhaps Aquinas is thinking of the infallibility of the Church guided by the Holy Spirit (John 16:13).

Revised March 2012