This article contributes to the historiography of scientific objectivity as well as to the broader attempt to historicize basic epistemic categories by examining the case of empirical psychology in eighteenth-century Germany. From the time when the philosopher Christian Wolff first presented empirical psychology in the late 1720s until Kantian philosophers elaborated on the topic towards the end of the century, the discourse hinged on discussions of how to obtain scientific knowledge of the soul. Whereas the work of Wolff and his (...) followers reflected established epistemic techniques for accomplishing this, from the early 1770s philosophers highlighted a new category of difficulties connected to the development of a systematic method of psychological self-observations. These difficulties, I argue, both complement and complicate the picture of how the subject became an obstacle to knowledge first in the mid-nineteenth century. (shrink)