ions performed by the
bodily organs with external objects would not have resulted unless the
objects had been present to operate or to be operated upon, clearly
there must be resident in, or inseparably bound up with, the objects a
power or powers of producing sensation in conscious mind. But the power
of producing sensation, and sensation itself, are not one and the same
thing, but two separate and distinct things, intrinsically distinct and
locally separate. The feeling, agreeable or painful, according to its
intensity, which heat occasions, is not the same thing as the heat by
which it is occasioned. The twofold taste, sweet to a healthy, bitter to
a distempered palate, of one and the same aliment, cannot be identical
with the single property of the aliment whereby the taste is produced.
In the sense of seeming red to a spectator with normally constructed
eyes, and green to one who is colour-blind, a ruby or a Siberian crab is
at once both red and green, but the two colours which it causes to be
perceived cannot be identical with the peculiar structure, or whatever
else it be, whereby the ruby or Siberian crab communicates to
circumambient ether the one self-same motion that terminates in
different impressions on differently constructed eyes. In these and in
all cases of the kind the feeling is in the mind, the source of the
feeling in matter. The one is a perception, the other a quality, and to
mistake the quality, not merely for a perception, but for the very
perception to which the quality gives rise; and to infer thence that the
quality must likewise be in the mind, is an instance as glaring as can
well be imagined of that most heinous of logical offences, the
confounding of cause with effect.

By what steps Berkeley was led, and has since led so many after him,
into so grave an error, he has himself acquainted us. Thus it is that he
argues: By sensible things can be meant only such as can be perceived
immediately by sense: and sensible _qualities_ are of course sensible
_things_. But the only perceptions of sense are sensations, and all
perceptions are purely mental. Wherefore, sensible qualities being, as
such, perceptible immediately by the senses, must be sensations, and
being sensations must be perceptions, and being perceptions they are of
course purely mental, and existent nowhere save in the mind. Carefully,
however, as Berkeley fancied he was picking his way, he really had
tripped, and that fatally, at t