igo 
Animal Automatism . 
[April, 
and the mass of grey and white matter which the brain of 
another presents to him, is, like the rest of the “ external 
world,” a mere subjective phenomenon. But each individual 
is justified by analogy in assuming the existence of other 
individuals, who manifest their thoughts and sensations in 
the same way in which he manifests his own. The physio- 
logist or physician is therefore practically an observer of two 
sets of phenomena — those which belong to the physical 
frame of the patient, and those which belong to his mental 
constitution. The latter kind of observation is, of course, 
only mediately possible ; but the faCts of which it takes note 
may be sufficiently interpreted by the experience and self- 
knowledge of the investigator. He will discover that all 
changes in the latter class are preceded by certain definite 
changes in the former, and will at length arrive at the con- 
clusion that the mind “ is really a system of effects, the 
causes of which are to be sought in antecedent changes of 
the matter of the brain.” * He will next remember that, as 
shown above, every thinker is forced to postulate the reality 
of “ mind-stuff,”— that is, of a matrix which generates the 
phenomena of sensation and thought. If not misled by 
genius, he will see the necessity of ascribing the invariably 
preceding phenomena of matter and motion to the same 
creative proplasm, since he is not entitled to assume the 
existence of any other. Since these latter phenomena are 
by common consent called material, he is justified in as- 
signing to the proplasm of mind the familiar name of 
matter. Thus we may say of the brain, “ Cogitat , ergo est .” 
This monistic view is preferable, not merely from its con- 
venience as a “ working hypothesis,” but because it contents 
itself with asserting the being of that matrix whose non- 
being is unthinkable, and declines to take any note of an 
“ immaterial substance,” for the existence of which, as 
Prof. Huxley admits, not a particle of demonstrative evidence 
can be offered. The attitude of a Materialist towards the 
“ anima ” is that of every modern astronomer towards those 
planetary genii, or “ ruling spirits,” which were finally dis- 
established by Kepler from their crystal spheres. The 
existence of such beings “ cannot possibly be disproved,” 
and no reason can be given for disbelief in them, save their 
total superfluity. 
Let us, then, assume our material proplasm as the vera 
causa of mental and physical phenomena, and see how this 
theory agrees with recognised fadts. In the first place, we 
* Life of Hume, p. 78. 
