Aquinas’ Cosmological Arguments

Aquinas’ Cosmological Arguments

The Cosmological Argument for the existence of God, as propounded by

Thomas Aquinas, is also known as the Third Way. It is the Third of

Five ways in Aquinas's masterpiece, "The Summa" (The Five Ways). The

five ways are: the unmoved mover, the uncaused causer, possibility and

necessity, goodness, truth and nobility and the last way the

teleological.

The first three ‘ways’ are different variations of the cosmological

argument.

The Cosmological argument is developed around a distinction between

that which has necessary existence and that, which is contingent. A

thing that has necessary existence must exist in all possible worlds,

whereas a thing that is contingent may go out of existence.

The method Aquinas uses is to set up the contrary position, then prove

it to be wrong. Therefore, the cosmological argument begins by

accepting the premise that all things are contingent. If all things

are contingent, i.e., if all things can go out of existence and do not

necessarily exist, then there must be a time where all things go out

of existence.

The basic idea is that everything has a prior cause, but the chain of

causes can't go back infinitely far, so there must be a first cause.

The "first way" (Unmoved mover) argument might be summarized like

this:

1. Some things change. (Empirical premise, verified by observation)

2. Everything that changes is made to change by something else.

(Aquinas has a separate argument for this)

3. The chain of causes can't go back to infinity.

4. Therefore, there must be a cause of change that does not itself

change.

Premise 2, that everything tha...

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...g’ have no consistent

meaning. Any being claimed to exist may or may not exist. Hume stated

this by saying that ‘all existential propositions are synthetic.’ He

believes all statements about existence need evidence.

He thinks if ‘necessary being’ means only ‘imperishable being’, then

the universe itself may be necessary. This is similar to Russell’s

point in this debate with Copleston.

Hume also thinks no proposition about existence can be logically

necessary. The opposite of any statement about experience is always

perfectly possible. This may rest on confusion, as Aquinas does not

claim that God’s existence is logically necessary – instead he claims

that the existence of God is necessary given motion, cause, and

contingency. God is not logically necessary – God is de re necessary,

necessary in and of himself.