The First Cause Argument (Cosmological Argument)

The first cause argument (cosmological argument) reasons that everything that exists must have a cause, and that the chain of causes cannot go back infinitely — there must be a first, uncaused cause, which is God. This lesson explores the argument, its history, and its strengths and weaknesses.

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What is the First Cause Argument?

The cosmological argument (from the Greek kosmos meaning "world" or "universe") can be summarised:

1. Everything that exists has a cause
2. The universe exists, so it must have a cause
3. There cannot be an infinite chain of causes (infinite regress)
4. Therefore, there must be a first cause that is itself uncaused
5. This uncaused first cause is God

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St Thomas Aquinas (1225-1274)

The most famous version was developed by the medieval philosopher and theologian Thomas Aquinas in his "Five Ways." The relevant ways are:

The First Way — The Unmoved Mover

• Everything in motion (change) was set in motion by something else
• This chain cannot go back forever — there must be a first mover that is itself unmoved
• This unmoved mover is God