— all these we shall explain, on their physical side, by tracing them to the central modes of neurosis corresponding to the similar central processes of seeing and hearing and of thinking in general.
The traditional views of our subject are natural to the historical course and unfolding of human thought. Following the latter, it is easy to see how and why pleasure and pain were set apart as attributes of our other mental elements rather than classed in common with them. On the other hand, the views herein to be offered are in accord with the modern notions of strict correspondence between all psychic phenomena and their neural basis, and of the origin of our whole nervous system, embryonically from a common cell, and biologically through a common process of development. These two truths — the naturalness of the traditional doctrines and of their errors to the historical development of science and of philosophy, and the harmony of the views herein to be advocated with the latest teachings of various sciences in their unanimity — these truths we shall, as we go on, seek to make plain and elucidative of each other.
Bearing our two hypotheses in mind, let us begin with the most immediate kind of evidence and work our way outward. To me a pain, while I have it, is as disparate as the color blue while I see that. With a pin I touch certain points on the back of my hand in the slightest possible manner. Long after the visible touch is made, a sharp definite pain comes swelling in, out of all proportion to the pin-touch and entirely unaccompanied with any other resulting sensation to be discovered by the closest scrutiny. Again, prick harder; the feelings of touch and of pressure will soon vanish, while the sharp pain will remain alone for some seconds. Moreover, when I prick gently, I get slight, when harder, more pain; there is no passing into pleasure, be the touch or pressure on these precise points as gentle as it may be. All this is more evident upon stimulation of certain isolated nerves or nerve trunks mechanically or electrically. Then we frequently have 'floating pains,' which we can neither locate precisely nor attach to some other sensation
