Aquinas and Anselm on natural theology (read also “Causa Prima” in the course packet)

Aquinas’s First Way:

The syllogism (see also Re Aquinas's Five Ways):

1. God is the First Mover

2. The First Mover exists

Therefore, God exists

Proof of premise 2.

1. Something is moved (is in motion)

2. Whatever is moved is moved by something else

3. If everything that moves is moved (i.e. the series of movers and moved things goes to infinity, which is to say that every mover is a secondary mover), then there is no First Mover

4. If there is no First Mover, then no secondary movers move (since secondary movers move only if moved by the first)

5. If no secondary movers move, then nothing is moved

Therefore, there is a First Mover (and there is only one, as can easily be proved), i.e., the First Mover exists

[Note: a First Mover here is something that moves, but is not moved, which is why it is first in the series of movers and moved things.]

Proof of premise 2.

1. Whatever moves is in actuality in respect of that towards which it moves.

2. Whatever is moved is in potentiality in respect of that towards which it is being moved.

3. Nothing can be both in actuality and in potentiality in the same respect.

Therefore, nothing can be both a mover and a moved thing in the same respect.

The most important thing to understand about this argument is what sort of series of “movers”, or more generally, efficient causes, Aquinas has in mind here. We can see why several apparently plausible objections are in fact invalid only if we clearly understand that this series consists of *per se, actual, efficient causes arranged in an increasing order of universality.*

The requirement of per se agency is obvious from the principle that a per se cause has in actuality whatever it causes in its per se effect, which has it in potentiality. This is why nothing can be a per se cause (mover) of itself in the same respect. (See also: per se vs per accidens)

The requirement of actual agency is obvious from the fact that a merely potential cause is not required for the actual maintaining of the effect. Therefore, from the actuality of an effect we can infer only the past existence of a cause. But here we need to conclude to the actual, present existence of a First Mover (First Cause).

Finally, the requirement of looking for ever more universal causes in this series should be obvious from the fact that whenever we arrive at the explanation of some particular effect in terms of the action of some particular agent, there always has to be some more general aspect of the activity of the agent which needs to be accounted for in terms of the activity of some more universal agent, which accounts not only for the activity of this particular agent, but a number of others as well, and it is in this way that we eventually have to arrive at a most universal agent that is responsible for the activity of all others in the most universal respect of all sorts of agency, namely, being, or existence itself.

Check again Saint Thomas’s “On the Principles of Nature” (see also: Definitions of Basic Concepts in Aquinas' Principles of Nature) for these distinctions. Try considering objections to the argument above and try to give their solutions in terms of these distinctions. Also, try to apply these considerations to the second and third “ways” of Aquinas’s text.

Having considered the relationships between the notions of causality, being and perfection, perhaps it will be easier to understand the import of “greater” in Saint Anselm’s argument. Obviously, “greater” in this context should be taken to mean “greater in perfection”, and hence “greater in being”.

St. Anselm’s argument

1. God = that than which nothing greater can be thought (TT) [nominal definition of TT]

2. TT is in the understanding (i.e., TT can be thought) [self-evident, unless the nominal definition of TT is contradictory, which would be tough to swallow]

3. TT is not in reality [assumption]

4. If something is in the understanding and not in reality, then something greater than it can be thought (namely, something that is in reality) [self-evident, based on the meaning of “greater”]

5. Something greater than TT can be thought, i.e., Something greater than that than which nothing greater can be thought can be though [2, 3, 4]

But 5. is contradictory, so one of the premises from which it followed has to be false. But it cannot be either of the self-evident premises, so it has to be the assumption, namely, 3. So, its denial, namely, that is TT is in reality is true; therefore, by 1. God is in reality, God really exists

The argument is obviously valid, still it is not convincing for an atheist. Try to explain how this is possible without assuming that being an atheist is some sort of mental defect. How can Aquinas’s criticism of Anselm explain his different approach to the problem?