cate ridges and furrows, like the surface of a newly-ploughed
field; and when the waves of light come dashing up against the ridged
surface, they are broken like the waves on a shingly shore, and are
flung backwards, so that they cross each other and the oncoming waves;
and, as every ray of white light is made up of waves of seven colours,
and these waves differ in length each from the others, the fairy
ridges fling them backward separately, and each ray reaches the eye by
itself; so that the colour of the mother-of-pearl is really the spray
of the light waves, and comes from arrangement of matter once again.
Give the dull, black wax the same ridges and furrows, and its glory
shall differ in nothing from that of the shell. To apply our
illustration: as the colour belongs to one arrangement of matter and
the dead surface to another, so life belongs to some arrangements of
matter and is their resultant, while the resultant of other
arrangements is death."[10]

The same line of reasoning naturally was applied to the existence of
"spirit" in man, and it was argued that mental activity, the domain of
the "spirit," was dependent on bodily organisation. "When the babe is
born it shows no sign of mind. For a brief space hunger and repletion,
cold and warmth are its only sensations. Slowly the specialised senses
begin to function; still more slowly muscular movements, at first
aimless and reflex, become co-ordinated and consciously directed.
There is no sign here of an intelligent spirit controlling a
mechanism; there is every sign of a learning and developing
intelligence, developing _pari passu_ with the organism of which it is
a function. As the body grows, the mind grows with it, and the
childish mind of the child develops into the hasty, quickly-judging,
half-informed, unbalanced youthful mind of the youth; with maturity of
years comes maturity of mind, and body and mind are vigorous and in
their prime. As old age comes on and the bodily functions decay, the
mind decays also, until age passes into senility, and body and mind
sink into second childhood. Has the immortal spirit decayed with the
organisation, or is it dwelling in sorrow, bound in its 'house of
clay'? If this be so, the 'spirit' must be unconscious, or else
separate from the very individual whose essence it is supposed to be,
for the old man does not suffer when his mind is senile, but is
contented as a little child. And not only is this constant,
simultaneous