First Cause

First Cause is a philosophical term introduced by Aristotle. Aristltle noted that causes in nature exist in a chain, stretching backward. The cause of the cat you see today was its parent cats, and the cause of those parents were the grandparent cats, and so on. The same for the oak tree you see — it was caused by an acorn from a previous oak tree, which in turn was caused by an oak tree from a previous oak tree, and so on, stretching back to whenever.

The question about such causal chains, raised by others, is whether they must have a terminus or starting point. Aristotle and others claim that the answer is yes, that there must be a First Cause because such causal chains cannot be infinite in length. Theists identify this First Cause with God, and use this argument, usually known as the argument from causation, as an argument for the existence of God.