1883.] The Brain Theory of Mind and Matter . 123 
precisely the same degree of validity, and that this validity 
is purely internal and individual. “ The whole universe of 
things and thought is thus only an automorphosis, each Ego 
being to itself, as Protagoras postulated, the measure and 
standard of all existing things, of all thought and objects of 
thought whatsoever.” * The profound Protagorean maxim 
is frequently attacked, with complete misapprehension of its 
import, by philosophers and scientists of the shallower sort, 
who appear to suppose that it implies an ignorant disdain of 
all existence which is not human, instead of a recognition of 
the solidarity between Man and the Universe, animate and 
inanimate, sentient and senseless. f A more than usually 
amusing example of this misconception is afforded by that 
popular writer Grant Allen, in a recent work reviewed last 
month in the “ Journal of Science.” It is evident, from his 
patronising approval of wind-fertilised flowers, and his vehe- 
ment attack upon the poppy, the convolvulus, and the 
“ unlovely ” Gloxinia, that if the mind of man in general 
cannot claim to be the “ measure of all things,” yet the 
mind of Mr. Grant Allen in particular conceives itself well 
entitled to that proud pre-eminence. 
Let us see in what sense every man is, to himself, the 
standard by which “ all thought and objects of thought ” 
must be tested and classified. A colour-blind person has 
perceptions which are quite as true as those of the most 
subtly discriminative landscape painter; but the retinal 
“ colour-box ” of the former has no tints corresponding with 
the green and crimson which the latter differentiates into a 
thousand delicate gradations. The unknown force which we 
call Light, and picture intellectually as a series of ethereal 
vibrations, without thereby advancing a step towards the 
knowledge of its essential nature, aCts impartially upon the 
retina of both. That its internal manifestations are diverse 
depends upon the special organisation of the two individuals. 
One has, and the other has not, colours in himself. Light, 
then, is not a simple gift from the sun, but is a product of 
mental metabolism, which fashions all that we know of 
brightness and darkness. Beyond this there is practically 
nothing, for our wildest imagination cannot overleap the 
boundaries of Self, and depict an invisible cause of Light. 
The very terms which we must use, if we wish to imply 
* What is Religion? p. 38. Appendix No. 1. 
f Even J. S. Mill, who in his definition of Matter as a “ permanent possi= 
bility of sensation ” virtually adopts the Auto-centric position, inconsistently 
condemns the axiom of Protagoras as “ a scandal to philosophers,” evidently 
quite misapprehending its real import. 
