Nineteenth-century scientist Hermann von Helmholtz’s peculiar wavering between empiricism and transcendentalism in his philosophy of science in general, and in his theory of perception in particular, is a much debated and well-documented topic in the history and philosophy of science. This contribution aims at providing a fresh angle on this classical issue, by considering Helmholtz’s account of differential consciousness against the background of a centuries-old philosophical debate between the empiricist tradition and the tradition of transcendental idealism. By placing Helmholtz’s psychology (...) against the background of a historical narrative stretching from Hume to Fichte, one can gain insight into the possible merits of his empirico-transcendentalism with regard to the problem of differentiation. More particularly, it is argued that Helmholtz’s psychology tilted towards transcendentalism when met with the classical theoretical problems of strict empiricism in dealing with the foundation of consciousness, most notably circularity and infinite regress. Without claiming that Helmholtz’s theorizing presented a self-conscious attempt to overcome the latter issues, his well-known wavering between perspectives in general, and his appropriation of the a priori in particular, might have served him well in avoiding the deadlocks of empiricism. As noted at the end, however, Helmholtz’s account produced complex philosophical problems of its own. (shrink)