The Anselmian Ontological Argument (from St. Anselm’s Proslogion, 11th century) is a philosophical argument for God’s existence based solely on the concept of God, without appealing to physical evidence.
Main Idea:
- Definition of God
- God is defined as “that than which nothing greater can be conceived” — the greatest conceivable being.
- Existence in Mind vs. Reality
- Even a fool (the skeptic) understands this concept when hearing the word “God,” so God exists at least in the mind (as an idea).
- But something that exists both in the mind and in reality is greater than something that exists only in the mind.
- Logical Conclusion
- If the greatest conceivable being existed only in the mind, we could conceive of a greater being—one that exists in reality as well.
- Therefore, by definition, the greatest conceivable being must exist in reality; otherwise, it would not be the greatest.
- Result
- God necessarily exists, not as a contingent being, but as a necessary one whose nonexistence is impossible.
1. Anselm’s Ontological Argument (Formal Syllogism)
- Definition of God
- God is “that than which nothing greater can be conceived” — the greatest conceivable being.
- Existence as a Perfection
- Existing in reality is greater (a perfection) than existing only as an idea.
- Conceptual Existence
- Even skeptics understand the concept of God when they hear it, so God exists at least in the mind.
- Contradiction if Only in the Mind
- If God existed only in the mind, we could conceive of a greater being — one that exists both in the mind and in reality.
- That would contradict the definition of God as the greatest conceivable being.
- Conclusion
- Therefore, the greatest conceivable being must exist in reality.
- God exists necessarily; His nonexistence is impossible.
2. Major Objections and Replies
1. Gaunilo’s “Perfect Island” Objection (11th century)
- Objection:
If Anselm’s logic works, we could prove the existence of any “greatest conceivable” thing — like a perfect island.
But imagining a perfect island doesn’t make it exist; so the argument is flawed. - Reply (Anselm & defenders):
- The argument applies only to a necessary being, not contingent things like islands.
- A “perfect island” can always be made “greater” (add more palm trees, beaches, etc.), so it has no intrinsic maximal greatness.
- God, by contrast, is defined as a being with necessary existence and maximal attributes (power, knowledge, goodness), which are not arbitrarily expandable.
2. Kant’s “Existence is Not a Predicate” (18th century)
- Objection:
- Existence is not a property that adds greatness to a concept; saying “God exists” does not add a new quality to the concept of God.
- You cannot define something into existence just by including existence as a trait.
- Reply (Defenders like Alvin Plantinga):
- The argument doesn’t treat existence as a simple property like “being tall” but as necessary existence — a mode of being.
- The argument claims that if it is possible for a maximally great being to exist, such a being must exist necessarily (Plantinga reformulates this using modal logic).
3. “Conceptual vs. Real Existence” Challenge
- Objection:
- Just because we can conceive of the greatest possible being doesn’t mean it exists outside our minds.
- You can imagine a perfect unicorn, but that doesn’t make it real.
- Reply:
- The argument’s force is in the definition: the greatest conceivable being cannot merely possibly exist; by definition, it must exist necessarily or not at all.
- If God is even possible, modal logic versions argue, then God must exist in every possible world (including ours).
Key Takeaway
The Ontological Argument is a “conceptual proof”: it doesn’t appeal to the world around us but to logic and the definition of God. Its persuasiveness depends on whether one accepts:
- The coherence of the concept of a maximally great being,
- That necessary existence is a meaningful property,
- And that modal reasoning can justify actual existence.