Catechism 101: The Argument from Contingency

In this episode, we continue our series on St Thomas Aquinas' Five Ways by exploring his Third Way: the Argument from Contingency.
Aquinas begins with a simple but profound observation: the things we encounter in the world don't have to exist. You exist, but you could have failed to exist. The same is true of trees, mountains, planets, stars, and everything else we encounter in the created world. Philosophers describe things like these as contingent beings.

But if everything were contingent, i.e. if everything depended upon something else for its existence, then what ultimately explains why…