The Kant–Frege view

After psychology and cosmology, Kant has a final chapter on theology. This treats three traditional arguments for God's existence, starting with the so-called ontological argument, which goes somewhat as follows.

If the word ‘God’ means, in part, ‘being which is omnipotent, benevolent, omniscient…’, then anyone who says ‘God is not omnipotent’ either contradicts himself or is not using ‘God’ with its normal meaning. Now, ‘God’ means, in part, ‘being which is existent, omnipotent, benevolent…’ That implies that anyone who says ‘God is not existent’ either contradicts himself or is not using ‘God’ in its normal meaning; whence it follows that ‘God is existent’, normally understood, is guaranteed as true just by the meaning of its subject-term.

Kant rejects this argument because, he says, ‘existent’ has no right to occur in a list of terms purporting to express what an item must be like in order to qualify for a certain label. Existent things are not things of a kind; existence is not a state or quality or process; ‘existent’ is not a predicate. ‘“Exist”… is a verb, but it does not describe something that things do all the time, like breathing, only quieter – ticking over, as it were, in a metaphysical sort of way.’

Kant puts this by saying that ‘existent’ is not a ‘real predicate’ or a ‘determining predicate’. It and its cognates can behave like predicates in a sentence, he admits, as when we say ‘Unicorns don't exist’, which may seem to report something that unicorns don't do. But that only qualifies it as a grammatical or ‘logical’ predicate:

Recall that a thing's ‘determinations’ are its properties or qualities. To ‘determine’ something is to discover or report detail about it.