52 LIFE: IT3 OR T GIN AND NATURE 
—just as the convex and concave surfaces of 
a sphere are but two expressions of an under¬ 
lying reality. As to the nature of this reality, 
Kant and Herbert Spencer were content to call 
it X, or the unknown, while Spinoza maintain¬ 
ed that it was God. 
Analogies which are held to support this doc¬ 
trine are, however, extremely defective; but the 
subject is too lengthy and technical'to elucidate 
in detail here. 
PSYCHICAL MONISM: This doctrine con¬ 
tends that consciousness is the only reality— 
the material world being external appearance 
only. Thoughts are causally connected, but 
not necessarily physical events. (This doctrine 
is thus the exact inverse of epiphenomenalism.) 
In refutation of this theory, it may be point¬ 
ed out that, if brain changes are thus caused 
by, or are the outer expression of, thought,— 
why not muscular changes, and in fact all phy¬ 
sical phenomena throughout the world every¬ 
where:—for we cannot rationally draw the line 
of distinction here. Such is the logical out¬ 
come of the theory—and has in fact been ac¬ 
cepted in this form by Fechner and others. 
While many philosophers are inclined to ac¬ 
cept this view, it may be stated that the phy¬ 
sical scientists are naturally repelled by it, 
and so is common sense. 
SOLIPSISM: The contention of this theory 
is that nothing exists save states of conscious¬ 
ness in the individual. Neither the material 
world nor other minds exist (save in the mind 
of the individual). This doctrine is so opposed 
