Aquinas' Third Way

Aquinas' third way deals with the concept of %%contingency and necessity%%. Again, Aquinas notes that %%everything that exists has the possibility of not existing%% (i.e. is it contingent -anything that depends on something else) and draws the conclusion that if this was true of everything in existence then nothing would ever have come into existence. This is because %%in order for contingent beings to exist, there has to be a non-contingent%% (i.e. necessary being) that brought everything else into existence. For Aquinas, this necessary being is 'God.'

The third way is taken from possibility and necessity, and runs thus. %%We find in nature things that are possible to be and not to be%%, since they are found to be generated, and to corrupt, and consequently, they are possible to be and not to be. But it is impossible for these to always exist, for that which is possible not to be at some time is not. Therefore, if everything is possible not to be, then at one time there could have been nothing in existence … it would have been impossible for anything to have begun to exist; and thus even now nothing would be in existence … which is absurd.' (Aquinas)

Aquinas states that %%all things in nature are limited in their existence%%. They all have beginnings and endings. Following this idea to its logical conclusion %%Aquinas notes that this means at one point in history nothing existed and that, even now, nothing would exist%% -which is plainly not the case.

A way of thinking of this idea is to consider the relationship of the parent and the child. Without the existence of the parent, the child cannot come into existence. Or, to put it in another way, the child is contingent on the parent for its existence.

'Therefore, not all beings are merely possible, but there must exist something the existence of which is necessary. But every necessary thing either has its necessity caused by another, or not. Now it is impossible to go on to infinity in necessary things which have their necessity caused by another, as has been already proved in regard to efficient causes. %%Therefore we cannot but postulate (suggest or assume) the existence of some being having of itself its own necessity, and not receiving it from another, but rather causing in others their necessity'%%, This all men speak of as God.' (Aquinas)

Aquinas states that %%the only possible solution to this dilemma is that something must exist that is unlike everything else in existence%% -in that it has no beginning and no end, in other words, it has necessary existence. %%The necessary existence is needed to bring about the existence of everything else%%. For Aquinas this being was 'God.'

Summary

1) In order for contingent beings to exist, there has to be a non-contingent being

2) All contingent beings are limited to their existence

3) The only possible solution to this dilemma is that something must exist that is unlike everything else in existence.