t it.

Sec. 7. The explanation of Nature (if it be admitted to consist in
generalisation, or the discovery of resemblance amidst differences) can
never be completed. For--(1) there are (as Mill says) facts, namely,
fundamental states or processes of consciousness, which are distinct; in
other words, they do not resemble one another, and therefore cannot be
generalised or subsumed under one explanation. Colour, heat, smell,
sound, touch, pleasure and pain, are so different that there is one
group of conditions to be sought for each; and the laws of these
conditions cannot be subsumed under a more general one without leaving
out the very facts to be explained. A general condition of sensation,
such as the stimulating of the sensory organs of a living animal, gives
no account of the _special_ characters of colour, smell, etc.; which
are, however, the phenomena in question; and each of them has its own
law. Nay, each distinct sensation-quality, or degree, must have its own
law; for in each ultimate difference there is something that cannot be
assimilated. Such differences amount, according to experimental
Psychologists, to more than 50,000. Moreover, a neural process can never
explain a conscious process in the way of cause and effect; for there is
no equivalence between them, and one can never absorb the other.

(2) When physical science is treated objectively (that is, with as
little reference as possible to the fact that all phenomena are only
known in relation to the human mind), colour, heat, smell, sound
(considered as sensations) are neglected, and attention is fixed upon
certain of their conditions: extension, figure, resistance, weight,
motion, with their derivatives, density, elasticity, etc. These are
called the Primary Qualities of Matter; and it is assumed that they
belong to matter by itself, whether we look on or not: whilst colour,
heat, sound, etc., are called Secondary Qualities, as depending
entirely upon the reaction of some conscious animal. By physical science
the world is considered in the abstract, as a perpetual redistribution
of matter and energy, and the distracting multiplicity of sensations
seems to be got rid of.

But, not to dwell upon the difficulty of reducing the activities of life
and chemistry to mechanical principles--even if this were done, complete
explanation could not be attained. For--(a) as explanation is the
discovery of causes, we no sooner succeed in assigning the causes of th