(2.) The cosmological idea, the idea of the world as including all phenomena (the object hitherto of cosmology).
(3.) The theological idea, the idea of God as the highest condition of the possibility of all things (the object hitherto of rational theology).
But with these ideas, in which the reason attempts to apply the categories of the understanding to the unconditioned, the reason becomes unavoidably entangled in a semblance and an illusion. This transcendental semblance, or this optical illusion of the reason, exhibits itself differently in each of the different ideas. With the psychological ideas the reason perpetrates a simple paralogism, while with the cosmological it finds itself driven to contradictory affirmations or antinomies, and, with the theological, it wanders about in an empty ideal.
(1.) _The psychological ideas, or the paralogisms of the pure reason._
Kant has attempted, under this rubric, to overthrow all rational psychology as this had been previously apprehended. Rational psychology has considered the soul as a thing called by that name with the attribute of immateriality, as a simple substance with the attribute of incorruptibility, as a numerically identical, intellectual substance with the predicate of personality, as an unextended and thinking being with the predicate of immortality. All these principles of rational psychology, says Kant, are surreptitious; they are all derived from the one premise, “I think;” but this premise is neither intuition nor conception, but a simple consciousness, an act of the mind which attends, connects, and bears in itself all representations and conceptions. This thinking is now falsely taken as a real thing; the being of the Ego as object is connected with the Ego as subject, and that which is affirmed analytically of the latter is predicated synthetically of the former. But in order to treat the Ego also as object, and to be able to apply to it categories, it must be given empirically, in an intuition, which is not the case. From all this it follows that the proofs for immortality rest upon false conclusions. I can, indeed, separate my pure thinking _ideally_ from the body; but obviously, it does not follow from this that my thinking can exist _really_ when separate from the body. The result which Kant derives from his critick of rational psychology is this, viz., there is no rational psychology as a _doctrine_ which can furnish us with any addition to our self-knowledge, but only as a _discipline_, which places impassable limits to the speculative reason in this field, in order that it may neither throw itself into the bosom of a soulless materialism, nor lose itself in the delusion of a groundless spiritualism. In this respect rational psychology would rather remind us, that this refusal of our reason to give a satisfactory answer to the questions which stretch beyond this life, should be regarded as an intimation of the reason for us to leave this fruitless and superfluous speculation, and apply our self-knowledge to some fruitful and practical use.