Fechner had worked out this fundamental theory ere he arrived at his psychological results. We find glimmerings of it so soon as 1835, in the attractive "Little Book on Life After Death," in the tract "On the Highest Good" (1846); enlarged views in "Nanna, or the Soullife of Plants" (1848); while the system appears full-fledged in "Zend-Avesta, or the Things of Heaven and the Hereafter" (1851); in 1861 he returned to it in his book, "On the Soul Question," occasioned by contemporary materialism, and in "The Three Motives and Grounds of Belief"; and in 1879 he reaffirmed and restated the position in the remarkable volume entitled "The Day View and the Night View." The essence of his teaching may be summed up in the thought that the material or external world is a half-truth, a concession to the sensuous, rather than an explanation of the psychical;
Consequently, the physical symbolizes the psychical. They are two faces of a single existence. Human research may, therefore, deal with the one or the other, and attain, as it has attained, great success. But the real problem centers in the relation between the two. Of this, physiological psychology is the science. You can, accordingly, pursue it quâ science, but you must never forget the larger setting in which it finds itself.
Proceeding to the psychology, then, note at once that Fechner envisages the problem rather as a physicist than as a physiologist. So, he suffers from his limitations, but gains in precision. Soul and body being a single existence, it is practicable to investigate their mutual functioning and to state the results as laws of nature, which, in turn, are no more than assemblages of observations concerning phenomenal