colours connected with sounds and special associations of ideas,
being unconscious of their peculiarities; but I cannot anticipate
these subjects here, as they all require explanation. It will be
seen in the end how greatly metaphysicians and psychologists may err,
who assume their own mental operations, instincts, and axioms to be
identical with those of the rest of mankind, instead of being
special to themselves. The differences between men are profound, and
we can only be saved from living in blind unconsciousness of our own
mental peculiarities by the habit of informing ourselves as well as
we can of those of others. Examples of the success with which this
can be done will be found farther on in the book.

I may take this opportunity of remarking on the well-known
hereditary character of colour blindness in connection with the fact,
that it is nearly twice as prevalent among the Quakers as among the
rest of the community, the proportions being as 5.9 to 3.5 per cent.
[1] We might have expected an even larger ratio. Nearly every Quaker
is descended on both sides solely from members of a group of men and
women who segregated themselves from the rest of the world five or
six generations ago; one of their strongest opinions being that the
fine arts were worldly snares, and their most conspicuous practice
being to dress in drabs. A born artist could never have consented to
separate himself from his fellows on such grounds; he would have
felt the profession of those opinions [5] and their accompanying
practices to be a treason to his aesthetic nature. Consequently few
of the original stock of Quakers are likely to have had the
temperament that is associated with a love for colour, and it is in
consequence most reasonable to believe that a larger proportion of
colour-blind men would have been found among them than among the
rest of the population.