natural that conversion may seem, we cannot be sure it is practicable,
before we have had experience of it.

Thus I seem to have answered the three objections above-mentioned; though
at the same time I am sensible, that few will be satisfyed with these
answers, but will immediately propose new objections and difficulties.
It will probably be said, that my reasoning makes nothing to the matter in
hands and that I explain only the manner in which objects affect the
senses, without endeavouring to account for their real nature and
operations. Though there be nothing visible or tangible interposed betwixt
two bodies, yet we find BY EXPERIENCE, that the bodies may be placed in
the same manner, with regard to the eye, and require the same motion of
the hand in passing from one to the other, as if divided by something
visible and tangible. This invisible and intangible distance is also
found by experience to contain a capacity of receiving body, or of
becoming visible and tangible. Here is the whole of my system; and in no
part of it have I endeavoured to explain the cause, which separates
bodies after this manner, and gives them a capacity of receiving others
betwixt them, without any impulse or penetration.

I answer this objection, by pleading guilty, and by confessing that my
intention never was to penetrate into the nature of bodies, or explain
the secret causes of their operations. For besides that this belongs not
to my present purpose, I am afraid, that such an enterprise is beyond the
reach of human understanding, and that we can never pretend to know body
otherwise than by those external properties, which discover themselves to
the senses. As to those who attempt any thing farther, I cannot approve
of their ambition, till I see, in some one instance at least, that they
have met with success. But at present I content myself with knowing
perfectly the manner in which objects affect my senses, and their