effort accompanies
every muscular contraction by which the limbs, or other parts of the
body, are moved. By its agency the fact of their movement is known;
while the direction of the motion is given by the accompanying tactile
sensations. And, in consequence of the incessant association of the
muscular and the tactile sensations, they become so fused together
that they are often confounded tinder the same name.

If freedom to move in all directions is the very essence of that
conception of space of three dimensions which we obtain by the sense
of touch; and if that freedom to move is really another name for the
feeling of unopposed effort, accompanied by that of change of place,
it is surely impossible to conceive of such space as having existence
apart from that which is conscious of effort.

But it may be said that we derive our conception of space of three
dimensions not only from touch, but from vision; that if we do not
feel things actually outside us, at any rate we see them. And it was
exactly this difficulty which presented itself to Berkeley at the
outset of his speculations. He met it, with characteristic boldness,
by denying that we do see things outside us; and, with no less
characteristic ingenuity, by devising that "New Theory of Vision"
which has met with wider acceptance than any of his views, though it
has been the subject of continual controversies.[1]

[Footnote 1: I have not specifically alluded to the writings of
Bailey, Mill, Abbott, and others, on this vexed question, not because
I have failed to study them carefully, but because this is not a
convenient occasion for controversial discussion. Those who are
acquainted with the subject, however, will observe that the view I
have taken agrees substantially with that of Mr. Barley.]

In the "Principles of Human Knowledge," Berkeley himself tells us how
he was led to those views which he published in the "Essay towards the
New Theory of Vision."

"It will be objected that we see things actually without, or
at a distance from us, and which consequently do not exist in
the mind; it being absurd that those things which are seen at
the distance of several miles, should be as near to us as our
own thoughts. In answer to this, I desire it may be considered
that in a dream we do oft perceive things as existing at a
great distance off, and yet, for all that, those things are
acknowledged to have their existence only in th