The development of a methodologically naturalistic approach to physiological and experimental psychology in the nineteenth century was not primarily driven by a naturalistic agenda. The work of R. Hermann Lotze and G. T. Fechner help to illustrate this claim. I examine a selected set of central commitments in each thinkers philosophical outlook, particularly regarding the human soul and the nature of God, that departed strongly from a reductionist materialism. Yet, each contributed significantly to the formation of experimental and physiological psychology. (...) Their work was influenced substantively by their respective philosophical commitments. Nevertheless, the evaluation of the merits of their specific proposals, Fechner's psychophysics and Lotze's local sign hypothesis respectively, did not depend upon sharing their metaphysical views regarding the human soul or the nature of God. A moderate, but significant, distinction between the contexts of discovery and of justification aids in understanding this balancing act. (shrink)