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Kant on the Ontological Argument

Kant’s objection

A concept can specify what an object would be if it existed, but analysis of that concept cannot establish that the object exists. “Existence” does not add a perfection or descriptive determination to the concept of God. It posits an object corresponding to the concept. Therefore the move from “God is conceived as necessarily existing” to “God exists” is illegitimate.

Textual location

Kant, Critique of Pure Reason, A592/B620-A602/B630, “On the impossibility of an ontological proof of God’s existence.” The decisive passages are A594/B622-A600/B628; “being is obviously not a real predicate” occurs at A598/B626.

The proof Kant is targeting

Kant’s immediate target is the rationalist proof associated especially with Descartes and Leibniz, framed through the ens realissimum, the being containing all reality. A simplified reconstruction is:

  1. God is the most real or all-perfect being.
  2. Necessary existence is a reality or perfection.
  3. Therefore necessary existence belongs to the concept of God.
  4. Therefore God exists necessarily.

An Anselmian version speaks instead of that than which no greater can be conceived. Kant’s wording does not perfectly match every version in the tradition, which is one reason the scope of his refutation remains debated.

Kant’s objections, step by step

1. Necessity in a judgment is conditional on the object’s being posited

“A triangle has three angles” is necessary in this sense: if a triangle is posited, its three angles cannot be denied without contradiction. It does not follow that a triangle must exist. Logical necessity connecting subject and predicate is not absolute necessity of the subject’s existence.

The ontological proof slides from:

If God exists, God exists necessarily.

to:

God necessarily exists.

The first may express what belongs to the concept; the second asserts that the concept has an object.

2. Denying the object is not denying one of its predicates

If one posits a triangle and then denies that it has three angles, one contradicts oneself. But one can cancel the triangle together with all its predicates without contradiction. Likewise, denying God’s existence does not posit a divine object and strip away one of its essential properties. It denies that anything instantiates the entire concept.

This is why defining a being as “that whose nonexistence is impossible” does not show that the definition has an instance.

3. Existence is not a real predicate

A “real predicate” determines or enlarges a concept: adding “red,” “powerful,” or “omniscient” changes what is being described. Existence does not add another descriptive feature. “God is” does not attach an additional property to omnipotence, wisdom, and the rest; it posits that an object with the specified predicates corresponds to the concept.

Modern logic often expresses the same distinction by treating existence through quantification - roughly, “there is at least one x such that …” - rather than as an ordinary first-order property possessed by an already identified object.

4. The hundred-thalers example

One hundred possible thalers and one hundred actual thalers contain the same number and conceptual determinations. Actual thalers do not contain an extra coin called “existence.” Yet they make a very different practical difference to one’s financial condition. The difference lies between concept and instantiation, not between two concepts with different lists of predicates.

The example does not claim that existence makes no difference. It claims that the difference is not an enlargement of the object’s concept.

5. Existential propositions are synthetic

If “God exists” were analytic, existence would add nothing and the proof would merely repeat what it had placed in its definition. If it is synthetic, its truth cannot be obtained simply by unpacking that definition. Either way, definition alone does not cross from thought to being.

6. Conceivability does not prove real possibility

Even if the concept of an all-real being contains no obvious formal contradiction, that establishes only logical possibility. The real possibility of an object generally requires conditions that connect the concept to possible experience. Because the ens realissimum exceeds possible experience, speculative reason cannot establish its real possibility and then infer actuality.

The most common misunderstanding

Warning

Kant is not arguing, “God lacks the property of existence.” He is arguing that existence is not the kind of property that could be included among God’s perfections and then extracted from the definition as an existential conclusion.

Why this critique controls the other proofs

The cosmological proof reaches an unspecified necessary being, then needs to identify it as the all-real God. That identification requires the claim that the concept of the ens realissimum uniquely entails necessary existence - the ontological step.

The physico-theological proof reaches, at most, an intelligent architect. To turn that architect into the necessary creator it borrows the cosmological proof, and through it the ontological proof. Thus the conceptual failure here propagates upward.

Limits and later debate

Kant’s criticism is devastating against any proof that simply treats existence as one more perfection. It does not automatically settle every later modal ontological argument. A defender may formulate the argument using possible worlds and necessary existence rather than an ordinary existence predicate. Critics then ask whether the key possibility premise - that a maximally great being possibly exists - is independently justified or simply contains the disputed conclusion in modal form.

The fair claim is therefore:

Kant exposes why no definition can straightforwardly manufacture existence. Whether every sophisticated ontological argument commits exactly that error is a further question.

Sources