Kant’s objections to Cartesian accounts of the mind in the first Critique often lead readers to assume that he endorses some form of materialism, but the discussion of psychological ideas serves, Kant claims, to “destroy completely all materialistic explanations of the inner appearance of our soul” (4:334). As the chapter shows, the Prolegomena makes a distinctive appeal to the regulative use of these psychological ideas to argue against psychological materialism, or the view that our psychological states can be explained in terms of materialistic grounds, and further buttresses – in a different fashion – the position that Kant develops in the ‘Paralogisms’ section of the first Critique.

Chapter 7 turns to the first two of the three metaphysical disciplines whose inferences and conclusions Kant discusses in the Transcendental Dialectic, namely, rational psychology and cosmology. We show how the four transcendental paralogisms and the arguments underlying the four antinomies of pure reason can be read as ‘necessary inferences of reason’ and how they result in the corresponding transcendental ideas. The chapter considers the paralogisms and the psychological ideas, discusses the role of transcendental realism in the paralogisms, looks at the derivation of the cosmological ideas and the four antinomies, and reconstructs the role of transcendental realism in the antinomies. In doing so, we concentrate on those aspects that are relevant to understanding how Kant develops his Rational Sources Account in the Transcendental Dialectic.