The One Possible Basis for the Proof of the Existence of the External World: Kant’s Anti-Sceptical Argument in the 1781 Fourth Paralogism

One of the most controversial (and least understood) parts of the Critique of Pure Reason is the Fourth Paralogism of rational psychology as presented in the 1781 First Edition (henceforth FP). Even interpreters who resist a phenomenalistic reading of the critical philosophy, whose main tenet is that appearances or phenomena in Kant’s system are to be understood as mental entities, very much like Berkeley’s ideas, commonly believe that the anti-Cartesian argument Kant presents in FP makes transcendental idealism nearly indistinguishable from the Berkeleyan esse est percipi; with the embarrassing consequence – noted by Kemp Smith – that Kant “refutes the position of Descartes only by virtually accepting the still more extreme position of Berkeley.” This dismissive judgment served as a serious obstacle for the appreciation of the extraordinary anti-sceptical resources Kant puts at our disposal there. The present paper intends to remedy this state of affairs and argues that, properly understood, FP contains the best strategy Kant ever adopted against scepticism in his fifty-year-long confrontation of this problem.