How Western Philosophy Attempts to Prove God's Existence Through Reason

Sharing how Western philosophy rationally proves God's existence. This is a logical dialogue spanning across time and space—quite fascinating.

Anselm's Original Proof

The first person to attempt proving God's existence through reason was Anselm.

Anselm: God is "the greatest conceivable being" that the human mind can imagine. If "the greatest conceivable being" exists only in the mind and not simultaneously in reality, then it would not be "the greatest conceivable being." Therefore, "the greatest conceivable being" must also exist in reality.

Objector: I can imagine "the greatest island," but does this island exist?

Anselm: "The greatest" can only be used to describe God.

Objector: ...

Thomas Aquinas's Proofs

Anselm's proof was controversial, so later Thomas Aquinas proposed more systematic "Five Ways":

1. First Mover: All motion requires an external force to initiate it, therefore there must be a first mover, which is God.
2. Causal Chain: The causes of all things trace back to an ultimate cause, and this cause is God.
3. Necessary Existence: All contingent beings require a "necessarily existing" foundation, and this foundation is God.
4. Source of Perfection: All things in the world refer to "absolute perfection," and this perfection is God.
5. Teleological: The order and purposefulness of the universe originates from an intelligent designer, which is God.

These proofs seem rigorous, but problems remain:

• The First Mover is challenged by modern physics (such as quantum mechanics)—not all motion requires external force.
• The causal chain and source of perfection can only prove an ultimate cause or perfect standard, but cannot directly equate to God.
• The universe doesn't necessarily have a "necessary existence," and all things don't necessarily have a clear purpose, so the premises of necessary existence and teleology are not necessarily established.

Descartes's Most Famous Proof

Descartes, famous for "I think, therefore I am," provided this logical proof:

Through universal doubt, Descartes established the certainty of "I think," proving the existence of self. He believed that the finite "self" cannot produce the "idea of an infinitely perfect God," and finite external things also cannot constitute such an idea. This idea can only originate from God's own existence; therefore, God must exist.

Kant later refuted this, saying "existence" cannot be treated as a property. Just because there is a concept of "a perfect God" doesn't prove this concept must exist in reality.