What is Anselm's ontological argument in its simple formulation, and why does it appear strange at first glance?

Anselm's ontological argument is one of the strangest philosophical arguments ever conceived. It states simply: God is "that than which nothing greater can be conceived." This greatest being either exists in the mind only, or exists in both mind and reality. But existence in reality is greater than existence in the mind alone. Therefore, if this greatest being existed only in the mind, we could conceive of a greater being (one that also exists in reality), which is a contradiction. Conclusion: God necessarily exists. The strangeness is obvious: how can we prove the existence of something in reality merely by thinking about its definition?

Inadequate Responses to Avoid

From some believers, hasty responses:

"The argument is clear and logical; whoever denies it denies obvious truths." This is unjustified haste. The ontological argument is one of the most controversial arguments in the history of philosophy. The greatest philosophers of the medieval period—Thomas Aquinas, for example—rejected it despite their deep faith. And Kant, one of the greatest philosophers of all time, provided a devastating critique of it. We cannot consider those who reject it as deniers of obvious truths.

"The argument proves God's existence definitively and finally." This is clear exaggeration. Even contemporary supporters of the argument—like Alvin Plantinga—do not claim it is a conclusive proof, but see it at most as an argument showing that belief in God is logically reasonable. Claiming it is conclusive harms the argument's credibility more than it helps.

From some atheists, superficial responses:

"I can prove the existence of a perfect island using the same logic." This is Gaunilo's famous objection from the eleventh century, but in its simple form it misses the target. The difference is fundamental: a perfect island is a limited possible being, while "that than which nothing greater can be conceived" is an absolute concept. The perfect qualities of an island (number of trees, type of sand) are relative and subjective, while absolute greatness is an objective concept in the argument.

"The argument is empty wordplay." This is hasty rejection. The argument raises deep philosophical questions about the nature of existence, the relationship between concepts and reality, and the limits of language and thought. Even if ultimately rejected, it deserves serious thought rather than mocking dismissal.

Why These Responses Are Inadequate

The common problem: failure to understand the argument's precision and philosophical complexity. The ontological argument is neither a magic trick nor a geometric proof, but a serious attempt to explore the relationship between concepts and existence. Criticizing or defending it requires dealing with complex philosophical questions: What is the nature of existence? Is it a property or not? What is the difference between possibility and necessity? These are not simple questions solved with a single sentence.

Serious Positions in the Debate

First, the classical Anselmian defense. Anselm himself, and his supporters throughout history like Descartes and Leibniz, see the argument as revealing a deep truth: the concept of God necessarily includes His existence. God is not a possible being who may or may not exist, but a necessary being. The argument, from this perspective, is not an attempt to prove the existence of something from nothing, but a revelation of what the concept of divinity itself entails.

Second, the influential Kantian critique. Immanuel Kant provided the most famous critique of the argument: existence is not a property or perfection added to a thing. Saying "God exists" adds nothing to the concept of God, but affirms that this concept has a referent in reality. One hundred imaginary dollars and one hundred real dollars have the same properties—the difference is that the latter actually exist. This critique changed the course of philosophical discussion about the argument.

Third, the contemporary logical formulation. Alvin Plantinga provided a new formulation using modal logic: if God's existence is possible (in at least one possible world), then it is necessary (in all possible worlds). This formulation shifts the debate to the question: is the existence of the "greatest possible being" logically possible? Plantinga admits the argument does not compel the non-believer, but shows that belief is reasonable.

Fourth, the contemporary critical position. Philosophers like Graham Oppy provide technical criticism: even if we accept the argument's logic, it depends on prior assumptions about the nature of necessity and possibility that may not be correct. Others see the argument as proving at most the necessity of a logical concept, not the existence of an actual being.

Where We Stand in This Debate Today

The ontological argument remains one of the most interesting arguments in philosophy of religion. Even its critics acknowledge that it raises important philosophical questions. Today's academic consensus is that the argument, even in its strongest formulations, does not provide conclusive proof, but may contribute to a cumulative case. The philosophical value of the argument transcends the question of its success or failure—it forces us to think about the nature of existence, necessity, and possibility.

For Advanced Reading

If you want to delve deeper:
─ Intermediate level: The difference between Anselm's original formulation and the formulations of Descartes and Leibniz
─ Advanced level: S5 modal logic and Plantinga's contemporary formulation
─ "Ontological Argument" family page
─ Anselm's "Proslogion" chapters 2-4