A crítica de Kant ao argumento a priori: os limites da tese “a existência não é um predicado real” para objetar as vias a priori

Abstract

This study investigates Kant’s thesis on the predication of being, with an emphasis on the refutation of a priori proofs of God’s existence. The research is divided into two parts. In the first, I conduct a comparative analysis between the critique of the Cartesian a priori argument in Beweisgrund (1763) and the refutation of the ontological proof in the Critique of Pure Reason (1781). Since the thesis that “existence is not a predicate” is already formulated in 1763, I assess whether it can indeed be considered the core of Kant’s objection to a priori proofs, as various commentators examined here argue. To address this question, I analyze the similarities between the reasoning in these two periods and show, in six interdependent subsections, how the objections to the a priori argument were already extensively developed in the pre-critical work. However, a crucial difference emerges: in 1763, Kant still proposed his Only Possible Argument for a demonstration of God’s existence. Thus, I conclude that the thesis of the non-predication of existence cannot, under any hypothesis, be taken as the core of the refutation. In the second part, I examine the issue of the modes of being (possible, actual, and necessary) and their relationship with knowledge based on a priori concepts. I construct a debate between Paton and Kemp Smith to address the interpretative challenges of the Postulates of Empirical Thought in General. Based on this, I revisit the Only Possible Argument and highlight the transformation in the comprehension of the modes of being. I find that, in 1763, Kant already rejected the logical foundation as a sufficient reason for existence but still proposed an a priori foundation in which internal possibility presupposed absolutely necessary existence. With the critical turn, this path of grounding is abandoned: obtaining necessary existence from internal possibility becomes unsustainable, as theoretical knowledge is now limited to possible experience. Finally, I return to the Ideal of Pure Reason to determine whether this text merely reiterates the pre-critical objections to the Cartesian-type argument or whether it provides new objections that enable the refutation of all a priori proofs. I analyze the three objections and show that, although there is no substantial innovation regarding the 1763 refutation, there are textual elements — particularly in the redefinition of the modes of being — that allow for the rejection not only of the Cartesian argument but of any a priori proof of existence. Thus, I argue that the refutation of a priori proofs is not centered on the thesis of the non-predication of being or any other specific objection. Consequently, I pave the way for a deeper comprehension of the role of critical presuppositions concerning metaphysics as a speculative discipline.