Elements of Psychophysics, Vol. I

...these activities original: "Thätigkeiten" only through the mediation of nerve conduction to our brain. Our entire mental activity has a direct activity in our brain dependent upon it, carries such activity with it directly, or draws such activity directly after it, from which effects then pass into the external world through the mediation of our nervous and motor organs.

The mediated functional relationships between body and soul The author uses "soul" (Seele) in a way modern readers might interpret as "mind" or "consciousness." fulfill the concept of functional relationship completely only insofar as one considers the mediation as part of the relationship, since if the mediation were removed, the constancy or lawfulness in the relation of the body and the soul—which exists with the presence of mediation—would disappear. Thus, a stimulus triggers a sensation according to a law only insofar as the living brain does not lack living nerves to transplant the effect of the stimulus to the brain.

Insofar as the mental original: "Psychische" is regarded as a direct function of the physical, the physical can be called the carrier or the foundation of the mental. Physical activities that are carriers or foundations of mental ones, and thus stand in a direct functional relationship to them, we call psychophysical.

The question of the nature of psychophysical activities, that is, regarding their substrate and form, is set aside from the beginning, and no assumption is made about it. Indeed, this can initially be set aside for two reasons: first, because in establishing the general foundations of psychophysics, we will be dealing with quantitative relationships just as in physics, where qualitative relationships are first made dependent on quantitative ones; and second, because according to the following division of our teaching, we will not yet need to take any special consideration of psychophysical activities in the first part of it.

By the nature of the matter, psychophysics is divided into an outer and an inner branch, depending on whether the relationship of the mental to the bodily external world or the bodily internal world—with which the mental is in the closest relationship—is considered; or, in other words, into a theory of...