Abstract

It is not usual to think of Fichte as a logician, nor indeed to think of him as leaving a legacy that shaped the subsequent history of symbolic logic. But I argue here that there is such a legacy, and that Fichte formulated an agenda in formal logic that his students (and their students in turn) used to spark a logical revolution. That revolution arguably reached its culmination in the logical writings of Franz Brentano, better known as a founding figure of the phenomenological movement. In logical writings that were published only posthumously, but that were fully elaborated in the decade prior to the publication of Frege’s Begriffschrift, Brentano (together with his collaborator Anton Marty) developed a radically innovative logical calculus that was explicitly designed to overthrow the orthodox logical analysis of judgment and inference. At the center of this revolution was the notion of thetic judgment [thetische Urteil], a form of judgment upon which Fichte had insisted in the first published version of the Wissenschaftslehre, and which his students subsequently set out to accommodate within the framework provided by Kant’s general logic. But thetic judgment proved resistant to such assimilation, and it was left to Brentano to use the analysis of thetic judgment in his attempt to topple a long-standing logical tradition. In what follows I reconstruct the main episodes in this century-long drama in the logical theory of judgment. My discussion is divided into four sections. I begin with a review of Fichte’s most explicit call for logical revolution, together with his introduction of the notion of thetic judgment, set against the backdrop of an anomaly.