Abstract

I argue that Kant's refutation of Mendelssohn's proof of the immortality of the soul also refutes his own proof of the permanence of material substance. To evade this result, Kant would have had to rely on premises that can only be established empirically. This difficulty brings up deep and disturbing difficulties with Kant's theory of matter and body in his Metaphysical Foundations of Natural Science and suggests that his early Physical Monadology offered a better account, one he was constrained by later commitments to abandon to the detriment of the coherence of his matter theory.