Philosophy
Anselm's Ontological Argument for God's Existence
Quick fact
Anselm first formulated this argument in 1078 in his work Proslogion, and it has been debated by philosophers such as Thomas Aquinas, René Descartes, Immanuel Kant, and Alvin Plantinga.
Why this is interesting
What if you could prove the existence of the most perfect being simply by thinking about it—without looking at the world at all?
Read the full explanation
Understanding Anselm's Ontological Argument for God's Existence
Imagine you are thinking about the greatest possible being—something than which nothing greater can be conceived. That is Anselm's definition of God. Now, consider two versions of this being: one that exists only in your mind, and one that exists both in your mind and in reality. Which is greater? Clearly, the one that exists in reality is greater, because existence adds a perfection. So, if God exists only in the mind, then we could conceive of a greater being—one that also exists in reality. But that contradicts the definition of God as the greatest conceivable being. Therefore, God must exist in reality. The argument is a priori: it does not rely on observation of the world, only on the concept of God.
A deeper explanation
The mechanism of Anselm's argument hinges on the idea that 'existence is a perfection'—a property that makes a thing better. It attempts to show that the very concept of a greatest possible being entails its necessary existence. The argument's significance lies in its bold claim that we can deduce reality from pure thought. However, critics like Gaunilo argued that the same logic could prove the existence of a perfect island. Immanuel Kant later objected that 'existence is not a real predicate'—that adding existence to a concept does not create a better concept. Despite these criticisms, the ontological argument has been revived in modern forms, such as Alvin Plantinga's modal version, demonstrating its enduring philosophical importance. Understanding this argument reveals how deeply our concepts can shape our beliefs about reality, and why careful logical analysis is essential in philosophy.