I will first consider his five proofs of Gods existence, then look at his account of God’s composition and then finally attend to his views on God’s power. It will be useful to briefly examine Thomas’s life and career first however, as a means to understanding the context from which his ideas emerge. St. Thomas Aquinas was was born in 1225 at Roccasecca, halfway between Rome and Naples. He completed his studies in Paris and from there spent much of his early life living in different domminican centres throughout Italy with the Mobile Papal Court.
He died in 1274 on route to the council of Lyon. Aquinas was remarkable in that he was convinced that the existence of God could, and should be proved by rational philosophical investigation rather than by faith alone. He believed that Aristotle’s ideas and methods were appropriate for Christianity and that the latter would even benefit from the former. In his Metaphysics he incorporates the Aristotelian ideas of potency, act, matter, form, essence and existence and uses these to provide proof of Christian teachings.
Aquinas believed that it was ridiculous to reject our rational capacities, and that reason was a competent tool for investigating the secrets of the universe. Aquinas is particularly well known for making a distinction between philosophy and theology (a distinction many of his contemporary scholastics would have felt disinclined to make) and for stating there were two types of knowledge, that obtained through reason and that obtained through faith.
Importantly Aquinas does not consider God’s self-existence to be self-evident to humans despite St Anselm’s famous argument. Anselm had written that if one truly understands God as “that than which nothing greater can be conceived” then God must necessarily exist as the alternative is logical contradiction. But Aquinas does not consider this as proof enough, according to Aquinas, just because one understands “that than which nothing greater can exist” does not mean that the idea of God actually exists, only that it exists psychologically in the mind of the believer.
With this in mind, he set out to prove Gods existence using a purely rational, philosophical approach. He gives five proofs of Gods existence; the first three having their basis in cosmology, the forth appealing to a natural hierarchy in nature, the last, commonly known as the argument from design. The basic form of his arguments is modus ponens; he presents premises, which if proven to be true, confirm the existence of the conclusion. The idea being that there are attributes of the world which cannot be explained except through God.
The first argument is the argument from motion which has its roots in Aristotle’s account of cause and effect. He points out that, according to his empirical senses, some things are certainly in motion or in the course of changing. Referring back to Aristotle, Aquinas accounts for change as the actualisation of potentiality, for example, water has the potential to be boiling hot but this potential must first be actualized. Further more, he presumes that an item in motion is caused to be in motion by something else, namely something in actuality. Causing change brings into being what was previously only able to be, and can only be done by something which already is” (SPW p200) Aquinas then states that to be in a state of actuality and potentiality at the same time and in the same respect is impossible since this would mean that that thing was both its own cause and effect. Essentially what he is saying is that things in motion cannot be responsible for that motion. Thomas next points out that this chain of causes and effects cannot go on forever since then there would be no first cause for the effect.
If there is motion then there must have been a first mover. “So we are forced to eventually come to a first cause of the change not itself being changed by anything, and this is what everyone understands by God” (SPW p200) There is space for criticism here though, Aquinas supposes that something can be made to be X only through the intervention of something actually X, when in fact, there seems to be any number of examples which could disprove this, for example dead men do not commit murders and Kingmakers need not be kings.
With this in mind there seems no reason to refute the idea that something could actualise its own potential. Moreover, why cannot there not be an infinite regress of cause and effect, infinite regress should hardly be more absurd an idea to us humans than the idea that there is a supreme and invisible being responsible for our creation. Additionally, if nothing causes itself, then how can there even be a first cause? We might reply in Aquinas’s defence that he meant that only something actual will bring about a change to being X in something which is potentially X.
The second argument is commonly referred to as the argument from efficient causality. Aquinas states that in the world around us, we can see an order of causes. Aristotle considered efficient cause to be the changer of that which is changed, Aquinas states that since causes are naturally ordered (cause and effect) it is impossible for efficient causes to stretch into infinity: there must be one first efficient cause, namely God. The third argument to prove God’s existence is taken from possibility and necessity.
He explains that some of the things we see in existence in nature need not exist, these generated and perishable things might grow from the soil and then eventually rot and decompose for example. Since, these items need not be, Aquinas infers that at an earlier stage, there must have been nothing at all and if that was true, then there would be nothing in existence today, moreover, given an indefinite amount of time, perishable items will always not exist eventually. He reasons then that there must be some ungenerated and imperishable items in the universe, otherwise, since nothing can come from nothing, nothing would exist.
Basically he is appealing once again to the idea of an efficient cause, it is not enough that everything is merely possible, there must be some necessary existence and this, he says is what we call God. We might consider Aquinas’s cosmological arguments to assert that God is a sustaining rather than an instigating force and is as such, outside of the causal chain. Nevertheless, how is it that something outside of the causal chain could effect something inside it in the first place? The forth argument deals with grades of being.
Qualities of being in nature are apparent in different values, if wisdom for example exists, then there are people who are wise as well as people who are less wise. Aquinas argues that there must be something that possesses the greatest wisdom as this is the standard we measure wisdom against. It follows then that there must be something greatest, or most perfect, in being. “There is something which is truest, and best, and most excellent of things and hence the most fully in being; for Aristotle says that the truest things are the things most fully in being” (SPW p201)
Furthermore, Aquinas believes that the greatest example of a quality must be the cause of that quality. God then is necessarily in existence as the most perfect being. The last argument for the existence of God is the argument from design. Aquinas notes that there are intelligent and intelligible beings in the world which behave purposely. Aside from these beings, there are also unintelligent beings which, despite their obtuseness appear to display the same purposeful behaviour. Aquinas is talking here about the non human world; birds build nests, the sea provides us with fish as food etc.
His point then is that in order for there to be purposeful activity from unintelligent creatures there must be an intelligent being who has created this agenda and who is responsible for directing it: this he calls God. For Aquinas, God is his own existence, he refutes the idea however that he is a body seeing as how a body requires a mover in order to move, and God is the first mover. Furthermore, according to Aquinas, God is wholly actual (purus actus), with no potentiality since otherwise God would require a causer to actualise its potentiality.
God must be fully actual unlike the human being who always has potential and so can never be fully actual, in this way, all physical things aim to emulate God’s pure actuality. Also, god could not have a body and still be most noble since a body is less sublime than the soul which animates it, so God, whom is the most noble of all things, cannot be a body. The implications of this are as follows, if god were merely a first material principal, God, like all material things would be merely potentiality and as such imperfect; God being the first efficient cause however means that God is perfect in every way.
Moreover, all perfect things that exist must be caused by God according to Aquinas as all perfections in items are due to their pre-existence in the efficient cause. We know God from the perfections that are poured out from him into creatures, and exist in him in a way surpassing the way they exist in creatures” (SPW p220) In order to fully appreciate Aquinas’s interpretation of the composition of God it will be useful to briefly examine his explanation for the composition of the world. Like Aristotle, Aquinas believes physical things to be a synthesis of matter and form.
Form is what makes something particularly itself or that kind of thing, while matter is that material which the form is fabricated from. The form of the sculpture is consistent despite changes in matter; for example a piece of wood sculpted into a piece of art remains wood. But Aquinas denies that God is composed both of form and matter instead calling him pure form. Aquinas diverges from Aristotle here however by explaining that this fundamental matter is without form; it is formless matter. To be matter, is to be potentially something, and as we have already seen, Aquinas considers God to be pure actuality.
Also since matter’s value is also dependent on its form, God cannot be matter since his value or goodness is not dependent on anything else. Since God is the efficient cause of everything, God must be pure form since whatever has matter can be influenced from another therefore the essence of God is form. We might ask then is Aquinas’s God some sort of pantheist ‘whole’, what makes god an individual in its own right? Aquinas clarifies his point by saying that the case of God as pure form without matter is an absolute anomaly. That matter cannot be host to God is exactly what differentiates it from other beings.
Moreover, Aquinas says that there is no pervading aspect of god in created things because god, as its efficient cause, cannot also be its form or matter. Essentially what he is saying is that God cannot be an ingredient in an item because no ingredient could be unconditionally primal among beings. Aquinas argues that while it would be incorrect to identify a human being (or any being with both matter and form) with its form because a human being is clearly more than its species, it is correct to identify God with his form seeing how this perfectly describes him.
In his account of metaphysics, Aquinas discriminates between essence and existence. A thing’s essence is that which makes the thing what it is, the fact that a thing exists then, is something else entirely: its essence then might be described as autonomous. While all corporeal, finite things have the potential to become existent from matter, Aquinas says that this could not be true of God since it has no potential to be actualized into existence in the first place. Aquinas asserts that God is not only its essence, but is also its existence. He means that God is definitively existent; to exist is included in the diagnosis of God.
It is worth remembering that because corporeal beings are divisible and hence composite and since Aquinas considers God to be incorporeal; he considers God to be simple. “Gods existence doesn’t differ from his substance” (SPW p204) For Aquinas, being and goodness are one in the same thing because what is desirable is that which is good. The distinction he says, is merely psychological. As we have said, that which is fully actual, is for Aquinas, fully perfect, since it is existence which makes something actual, then he concludes that God must be supremely good because it is prime existence.
Moreover, because God contains all perfections by its own essence, God alone is good essentially. This is not to say that other things do not have goodness, they have goodness as circumscribed by their form, this is analogous to God’s goodness but should not be absolutely identified with it. If a human being behaves in a sinful way, Aquinas blames it on an error in that persons ability to act, but God, since his will must be perfect, cannot sin by himself. Not only this, but according to Aquinas, God is not guilty either for the sins of others since their defective will has undermined God’s intention.
Although God did not cause the sin, he is, says Aquinas, free to punish those sinners who performed it so long as their punishment does not run counter to the highest good. “And our free choice causes sin by a lack of response to God. God then causes the free choice but not the sin” (SPW p293) Aquinas believes that matter makes forms finite, humans age and their bodies die because of the limits of matter. God then is infinite according to Aquinas because he is devoid of matter and because God is of infinite ability he is everywhere at all times.
But finite, composite things could never be said to be everywhere at all times because certain parts of it would be in one place while other parts would be in another and so the being as a whole could not be said to exist everywhere. Aquinas says that God alone reserves this power because he is the cause of these effects and does not administer the world indirectly. “Clearly then God is called omnipotent because he can do everything possible in itself” (SPW p249) It seems though that Aquinas believes it purposeful that human beings are finite because with infinite ability, there would be nothing left to aspire to.
Aquinas also believes that God is immutable, that is that he cannot change, he provides three proofs of this. Firstly he cannot change because God has no potential to do so, it is purely actual, secondly, that which is moved at once remains what it was and becomes something else, this means that the item being changed must be composite and God as we have already shown, is not composite. Finally, things that change take possession of something that they were not in possession of before, but God, who we have already shown to be infinite according to Aquinas, could not possibly become something that he is not, since he is everything.
God being infinite then, is also eternal, Aquinas considers time to be a way of measuring that which has a beginning and an end, but since God has neither, God is eternal. Moreover, God is essentially existence; therefore he is his own eternity. The other implication of God’s infinite existence is that there can only be one God, if there were several Gods then none of them could be infinite since they would not be responsible for the other’s perfection.
Aquinas accounts for the universe as some sort of hierarchy of being; firstly there is God, next come the angels, then humans, lesser animals and inanimate beings etc. and this chain of being is a central motif in his work. For Aquinas, God is only imperfectly describable through our language, our finite minds cannot comprehend God entirely, only paint an imperfect picture of him. It is as if he is telling us that the map we draw is still only a map, not the territory itself.