Whether God is Omnipotent: Thomas Aquinas

Aquinas' debate about God's omnipotence is found in his Summa Theologica. This is a vast work which covers a huge range of theological and philosophical issues. 

The structure of the Summa Theologica is somewhat like a discussion or debate, but without the drama of Plato's Dialogues. Aquinas began each topic by first posing a question (e.g. 'Whether God is omnipotent?'). Next he presented 'objections' to the idea. These objections might be scriptural, theological or philosophical in nature. After the objections he would write 'on the contrary' and then giving a piece of counter evidence to the objection. Aquinas' own view comes next prefaced with 'I answer that...'. Finally he systematically refutes or answers the objections that he previously set out.

The Question:

Whether God is omnipotent?

The Objections:

Objection 1: He cannot be because he is immovable [has no potential to change because he is fully actual already].

Objection 2: God cannot sin.

Objection 3: According to the collect (special prayer) for the tenth Sunday after Pentecost, God shows his omnipotence 'especially by sparing and having mercy'. However, there are things greater than these [so if this is the pinnacle of God's power then he is not very powerful].

Objection 4: The Bible says that God makes worldly wisdom look foolish by showing that what is thought to be impossible possible.

It may not be immediately apparent why abolishing necessity is a problem. However, in the Cosmological Argument Aquinas tried to demonstrate that contingent things (like human, the world etc) could not exist if there was not a necessary being to bring contingent beings into existence. Hence the problem with omnipotence resulting in a loss of necessity is that ultimately God would not exist and nor would anything else.

Thus the standard for knowing what is possible or impossible must come from God and not from the world.

If God were omnipotent then he would be able to do anything.

Thus there would be nothing that is impossible.

However, abolishing impossibility also abolishes necessity because something is necessary if it is impossible that is should not be so.

The Counter-claim:

On the contrary: It is said that "No word shall be impossible with God" (Lk. 1:37)

Aquinas' response:

I answer thatAll confess that God is omnipotent; but it seems difficult to explain in what His omnipotence precisely consists of.

Aquinas recognised that 'omnipotent' can be interpreted in different ways. He went on to explain that in his view it must mean that God can do all possible things. However, this does not yet give us complete clarity. What do we mean by 'possible'? Like the word 'omnipotent' both 'possible' and 'impossible' can have different shades of meaning.

According to Aquinas, when we talk of a thing being 'possible' we mean one of two things.

So far, so straightforward! Aquinas then elaborates further. Created things all have things that are possible for them to do given the type of thing that they are [think about the difference between what a fish, a tree and a human can do].  They also have things that are not possible to their type. However, God's power 'is infinite and not limited to any genus of being; but possesses within itself all being.' This means that whatever is possible for anything else is also possible for God. God has the powers of all beings. 

  1. Either that it is within the power of a particular person or group of people (Aquinas' uses the example of things that are within human power are possible to man).
  2. Alternatively, when we talk of possible we mean logically possible. Aquinas did not use the phrase 'logically possible' but talked of things being possible 'on account of the relation in which the terms stand to one another.' Aquinas' example of something that is possible by the relationship of the terms is 'Socrates sits'. An example of something which is impossible 'that a man is a donkey.'

Thus, when we speak of something being 'possible' we mean either

  1. It is in practice within the power of the particular agent.
  2. It is in theory something which can be done.

If we use the first definition of 'possible' (that it is within an agent's power) then this does not tell us anything very meaningful about God's power. God can do all humans can do and more. He can do everything that all created beings can do. Everything is within God's power and God can do whatever is within his power to do. However, Aquinas pointed out that this because a tautology 'God can do all that he can do'.

The second definition of possible is more helpful. He can 'do all things which are absolutely possible.'But God cannot do something when'the predicate is altogether incompatible with the subject.' (such as a human being a donkey).

'That which implies being and non-being at the same time is repugnant to the idea of an absolutely possible thing, within the scope of the divine omnipotence, not because of any defect in the power of God, but because it has not the nature of a feasible thing. Therefore, everything that does not imply a contradiction in terms, is numbered amongst those possible things, in respect of which God is called omnipotent: whereas whatever implies contradiction does not come within the scope of divine omnipotence because it cannot have the aspect of possibility. Hence it is better to say that such things cannot be done, than that God cannot do them.'

Aquinas' refutation of the objections:

Reply to Objection 1: God is omnipotent due to what he can do rather than what he cannot do. God's changelessness does not undermine his omnipotence.

Reply to Objection 2: To sin is to fall short of what should be achieved, to fall short is to fail to be omnipotent. Thus it is God's omnipotence is what prevents him from sinning and the inability to sin is not a lack.

Aquinas further suggests that God could sin if he chose to do so. However, this is a conditional proposition (IF he chose to do so THEN he could sin). The fact that God's omnibenevolent nature is such that he would never choose to do so means that in practise he would be incapable sin. Aquinas suggests the following analogy to make the point. 'If man is a donkey, he has four feet.' The fact that man is not a donkey obviously means that in actual fact he does not have four feet.

Reply to Objection 3: God's sparing and having mercy especially reveals God's omnipotence because it is a free act that shows God's supreme power. It is only because God is bound by no laws and has no superior that he is free to forgive and show mercy. God's mercy also leads people to do good which is the end point of all of God's power. Everything comes from God and thus God's sparing and having mercy is the foundation of everything else.

Reply to Objection 4: