exist apart from the mind? It is, I confess, quite as easy for me to
imagine that redness may exist apart from a visual sense, as it is to
suppose that co-existence, number, and distance can have any existence
apart from the mind of which they are ideas.

Thus it seems clear that the existence of some, at any rate, of
Locke's primary qualities of matter, such as number and extension,
apart from mind, is as utterly unthinkable as the existence of colour
and sound under like circumstances.

Will the others--namely, figure, motion and rest, and
solidity--withstand a similar criticism? I think not. For all these,
like the foregoing, are perceptions by the mind of the relations
of two or more sensations to one another. If distance and place are
inconceivable, in the absence of the mind, of which they are ideas,
the independent existence of figure, which is the limitation of
distance, and of motion, which is change of place, must be equally
inconceivable. Solidity requires more particular consideration, as it
is a term applied to two very different things, the one of which is
solidity of form, or geometrical solidity; while the other is solidity
of substance, or mechanical solidity.

If those motor nerves of a man by which volitions are converted into
motion were all paralysed, and if sensation remained only in the palm
of his hand (which is a conceivable case), he would still be able to
attain to clear notions of extension, figure, number, and motion, by
attending to the states of consciousness which might be aroused by the
contact of bodies with the sensory surface of the palm. But it does
not appear that such a person could arrive at any conception of
geometrical solidity. For that which does not come in contact with the