The Third Way: Argument from Possibility and Necessity (Reductio argument)
- We find in nature things that are possible to be and not to be, that come into being and go out of being i.e., contingent beings.
- Assume that every being is a contingent being.
- For each contingent being, there is a time it does not exist.
- Therefore it is impossible for these always to exist.
- Therefore there could have been a time when no things existed.
- Therefore at that time there would have been nothing to bring the currently existing contingent beings into existence.
- Therefore, nothing would be in existence now.
- We have reached an absurd result from assuming that every being is a contingent being.
- Therefore not every being is a contingent being.
- Therefore some being exists of its own necessity, and does not receive its existence from another being, but rather causes them. This all men speak of as God.