What is Kant’s Justification of Deduction? A Program for Reading the Critique of Pure Reason based on this Question

Commentators often debate the status of formal logic in the Critique of Pure Reason. They ask if Kant takes the laws of formal logic to be normative (telling us how we ought to think) or constitutive (denying formally invalid mental acts the status of thoughts). However, at a deeper level, commentators also ask whether Kant in fact justifies the science of formal logic in the Critique. The consensus, namely of Huaping Lu-Alder and Tyke Nunez, is that Kant not only cannot justify this science, but that the impossibility of doing so speaks in his favor. Nunez argues that Kant wisely recognizes the “logocentric predicament”, meaning that any proof of the necessity the laws of formal logic must rely on those same laws. Therefore, there can be no justification of the science of logic, as the science of the form of rational thought, in the Critique. I respond that this line of argument dangerously misinterprets the Critique in terms of 1) its relation to the Leibnizian tradition, 2) its internal argumentation, and 3) its overall significance. I argue instead that we must understand the Critique as, at heart, an entirely novel justification of the laws of formal logic and of logical necessity. First, in terms of Kant’s relation to the Leibnizians, I argue that the pre Kantian metaphysical tradition was intrinsically concerned with justifying the laws of logic. It wanted to show by this what it means to be a rational animal. For Kant, the virtue of the Leibnizians (especially Wolff) lay in making this effort systematically complete. Yet this systematization simultaneously demonstrated its fatal circularity. Wolffian metaphysics presupposed the logical laws that it justified. Therefore, Kant recognized that this logocentric predicament condemned it to failure, and he intended his Critique to justify the laws of logic in a novel way. Second, I argue that this interpretation makes good sense of the argumentation in the Critique. For Kant does not, like the Leibnizians, try to derive rules of thinking from ontological laws, but instead transcendentally reflects on the logical principles of how we try to prove anything at all. This is why he lists singular, infinite, categorical, hypothetical, and disjunctive judgments, along with their modality, in the Metaphysical Deduction: these are the essential elements of how we actively prove thoughts to be true or false. Moreover, this helps us understand Kant’s need for both the Transcendental Analytic and the Transcendental Dialectic. The former argues that we must be able to prove our thoughts true or false and derives transcendentally ideal principles of nature from that argument. The latter then proves that only cognition inherent to experience of nature is formally valid. Thus, by “bounding pure reason”, Kant demonstrates that we can justify logical necessity only for objectively valid cognition. This ‘bounding’ is his novel justification of the laws of logic and the science of formal logic based on them. It means that we autonomously constitute the logical structure of science qua science. This, I argue, is the significance of the Critique.