21. Explains how water felt as cold by one hand may be warm to the other.
Ideas being thus distinguished and
understood, we may be able to give an account how the same water, at the same time, may produce the idea of
cold by one hand and of heat by the other: whereas it is impossible that the same water, if those ideas were really
in it, should at the same time be both hot and cold. For, if we imagine warmth, as it is in our hands, to be nothing
but a certain sort and degree of motion in the minute particles of our nerves or animal spirits, we may understand
how it is possible that the same water may, at the same time, produce the sensations of heat in one hand and cold
in the other; which yet figure never does, that never producing--the idea of a square by one hand which has
produced the idea of a globe by another. But if the sensation of heat and cold be nothing but the increase or
diminution of the motion of the minute parts of our bodies, caused by the corpuscles of any other body, it is easy
to be understood, that if that motion be greater in one hand than in the other; if a body be applied to the two hands,
which has in its minute particles a greater motion than in those of one of the hands, and a less than in those of the
other, it will increase the motion of the one hand and lessen it in the other; and so cause the different sensations of
heat and cold that depend thereon.
