In the first book of the Transcendental Dialectic we find Kant’s criticism of four syllogistic proofs about the soul. On his view the proofs are formally invalid. Hence, as opposed to the view of their proponents – the rational psychologists – the inferences do not establish: (i) that the soul is a substance; (ii) that the soul is simple; (iii) that the soul is a person; (iv) that the soul can exist independently of material beings. Kant calls these fallacious proofs transcendental paralogisms.
The second paralogism, as presented and discussed by Kant in the A-edition of the KrV, is particularly intriguing and difficult. It is particularly intriguing because it is the most powerful and convincing of the paralogisms. It is to wit “the Achilles of all the dialectical inferences of the pure doctrine of the soul, nothing like a mere sophistical play that a dogmatist devised in order to give his assertions a fleeting plausibility, but an inference that seems to withstand even the sharpest testing and the greatest scruples of inquiry.” (KrV A351) It is particularly difficult because Kant’s dismissal of it is notoriously complex and suggests that the rational psychologist makes a number of quite different kinds of mistakes. Thus it is unclear how Kant’s critique of the second paralogism in the A-edition is supposed to fits with his general description of a transcendental paralogism in the same edition. The aim of this paper is to show that one can nevertheless extract a line of criticism against the rational psychologist, which shows that the rational psychologist involves himself in a formal fallacy that accords with the general description of a transcendental paralogism.
My argument will be developed in five steps. In the first step I argue that both of the two standard ways of rendering the logical form of the second paralogism in the A-edition are problematic since they overlook that the middle term of the proof involves a negation. Since for Kant negation can be of two kinds: finite or infinite, I present the hypothesis that the second paralogism is a formally invalid inference because of an ambiguity pertaining to the logical operation of negation. In the second step, I present the historical background of infinite negation and Kant’s version of it. In both versions, the crucial difference is that only mere negation (i.e., negative judgment in Kant’s parlor) is compatible with empty terms. In the third step, I use the distinction between negative and infinite judgment to present four different possible interpretations of the second paralogism. In the fourth step, I argue that according to Kant’s reconstruction of the rational psychologist’s argument he (the rational psychologist) in fact helps himself to a valid form of the proof that has an infinite judgment in the Minor. I then suggest that Kant’s critique of the rational psychologist is that he is not justified in using this valid form. Thus, contrary to his own assumption, the rational psychologist has at his disposal only the formally invalid form of the inference with a negative Minor. In the fifth step, I first show that my reading accords with Kant’s general description of a transcendental paralogism. I then argue that the error which underlies and indeed conceals the syllogistic fallacy, is that the rational psychologist assumes but has not shown that the soul as an object of pure rational psychology exists.