We cannot find the absolute basis of matter; we only know it
by its properties; neither know we the soul in any other way.
_Cogito ergo sum_ is the only thing that we _certainly_ know.

Why may not soul and matter be of the same substance (i.e.,
basis whereon to fix qualities; for we cannot suppose a
quality to exist _per se_, it must have a something to
qualify), but with different qualities?

Hamilton's analysis of the Absolute, once learned, was never
forgotten. It was a philosophic touchstone, understood by the
boy, applied by the man. With the Absolute, an entity stripped of
perceptible qualities, an "hypostatized negation," he could have no
traffic. The Cartesian motto of thought as the essence of existence
became another fixed point for him, and his last questioning phrase
half suggests the line of reasoning which, as he afterwards put
it, asserts that, philosophically speaking, materialism is but
spiritualism turned inside out.




III

MEDICAL TRAINING


At fifteen and a-half he began his medical training. Engineering, it
seems, was not within his parents' purview; the boy was thoughtful
and scientific; medicine was then the only avenue for science, and