But though motion and darkness, either alone, or attended with tangible
and visible objects, convey no idea of a vacuum or extension without
matter, yet they are the causes why we falsly imagine we can form such an
idea. For there is a close relation betwixt that motion and darkness, and
a real extension, or composition of visible and tangible objects.

First, We may observe, that two visible objects appearing in the midst of
utter darkness, affect the senses in the same manner, and form the same
angle by the rays, which flow from them, and meet in the eye, as if the
distance betwixt them were find with visible objects, that give us a true
idea of extension. The sensation of motion is likewise the same, when
there is nothing tangible interposed betwixt two bodies, as when we feel
a compounded body, whose different parts are placed beyond each other.

Secondly, We find by experience, that two bodies, which are so placed as
to affect the senses in the same manner with two others, that have a
certain extent of visible objects interposed betwixt them, are capable of
receiving the same extent, without any sensible impulse or penetration,
and without any change on that angle, under which they appear to the
senses. In like manner, where there is one object, which we cannot feel
after another without an interval, and the perceiving of that sensation
we call motion in our hand or organ of sensation; experience shews us,
that it is possible the same object may be felt with the same sensation of
motion, along with the interposed impression of solid and tangible
objects, attending the sensation. That is, in other words, an invisible
and intangible distance may be converted into a visible and tangible one,
without any change on the distant objects.

Thirdly, We may observe, as another relation betwixt these two kinds of
distance, that they have nearly the same effects on every natural