Aquinas' Three Ways

What are Aquinas’ Three Ways?

Arguments from motion, causation and contingency

What is Aquinas’ First Way?

The argument from motion

What is Aquinas’ Second Way?

The argument from efficient causation

What is Aquinas’ Third Way?

The argument from contingency and necessity

What is the First Way based on?

Objects move from potentiality to actuality

Why does Aquinas think motion requires God?

An Unmoved Mover is needed to begin the chain of motion

What is the Second Way based on?

Causes require a First Cause

Why does Aquinas reject infinite regress is the Second Way?

Without a First Cause no causes could exist

What is the Third Way based on?

Contingent beings require a Necessary Being

Why can’t contingent beings explain themselves?

Their existence depends on external factors

What is the Fallacy of Composition?

Assuming what is true of parts is true of the whole

Which of Aquinas’ Ways does the Fallacy of Composition attack?

All three ways

How does Hume challenge the First and Second Ways?

By questioning the assumption that every event must have a cause

Which Way is most vulnerable to criticism of necessary existence?

The third way

How does Russell challenge the Third Way?

The universe itself may be a brute fact

What is the strongest criticism of Aquinas overall?

He assumes causal principles can be applied to the universe as a whole

What is the strongest strength of Aquinas overall?

He provides a systematic explanation of existence and causation