The Paralogism of the Soul: Kant Against Rational Psychology

Kant describes a paralogism as an argument that appears valid but in fact relies on an unnoticed shift in meaning. In the First Paralogism, Kant examines how a rational psychologist mistakenly concludes that the soul is a substance by asserting that whatever cannot be thought except as a subject must therefore exist as a substance. The rational psychologist explains that the "I" of self-consciousness can only be thought of as a subject and never as a predicate. From these claims, they infer that the soul (understood as the thinking being) is a substance.

Kant argues that the rational psychologist's inference fails because it is ambiguous on the "subject." In the major premise, "subject" refers to something that is given in intuition, thus, falls under the category of substance which is a feature of objects in time. However, in the minor premise, "subject" refers solely to the logical role played by the "I think," which accompanies all representations and is not itself given in intuition. Because the "I" is never presented as an appearance in time, the category of substance cannot be applied to it. The rational psychologist therefore treats a logical feature of thought as if it were an ontological property of the soul, and the argument collapses once this shift is exposed.

Although Kant fundamentally rejects the rational psychologist's conclusion, he does not deny everything the rational psychologist claims. Kant believes that the "I think" must be the subject of all our representations and that this unity of apperception is necessary for experience. In this sense, Kant believes that the soul may be called a "subject." However, this logical characterization does not license a claim about the soul as a substance, something persisting in time, or as a simple and immortal entity. Those conclusions would require that the soul be given as an appearance in time, which it is not.

Kant's diagnosis of the rational psychologist's conclusion shows that the rational psychologist oversteps the limits of possible experience by applying the category of substance outside the domain in which it holds objective validity. Kant's first paralogism demonstrates how pure reason can be misled when it attempts to draw metaphysical conclusions from the form of self-consciousness. Kant ultimately grants that the unity of the "I think" is required for cognition, but it yields no knowledge about the soul as it is in itself.