out trial several of their operations
one upon another; as we do now the properties of a square or a triangle.
Did we know the mechanical affections of the particles of rhubarb,
hemlock, opium, and a man, as a watchmaker does those of a watch,
whereby it performs its operations; and of a file, which by rubbing on
them will alter the figure of any of the wheels; we should be able to
tell beforehand that rhubarb will purge, hemlock kill, and opium make
a man sleep: as well as a watchmaker can, that a little piece of paper
laid on the balance will keep the watch from going till it be removed;
or that, some small part of it being rubbed by a file, the machine would
quite lose its motion, and the watch go no more. The dissolving of
silver in AQUA FORTIS, and gold in AQUA REGIA, and not VICE VERSA, would
be then perhaps no more difficult to know than it is to a smith to
understand why the turning of one key will open a lock, and not the
turning of another. But whilst we are destitute of senses acute enough
to discover the minute particles of bodies, and to give us ideas of
their mechanical affections, we must be content to be ignorant of their
properties and ways of operation; nor can we be assured about them any
further than some few trials we make are able to reach. But whether they
will succeed again another time, we cannot be certain. This hinders our
certain knowledge of universal truths concerning natural bodies: and our
reason carries us herein very little beyond particular matter of fact.

26. Hence no Science of Bodies within our reach.

And therefore I am apt to doubt that, how far soever human industry
may advance useful and experimental philosophy in physical things,
SCIENTIFICAL will still be out of our reach: because we want perfect and
adequate ideas of those very bodies which are nearest to us, and most
under our command. Those which we have ranked into classes under names,
and we think ourselves best acquainted with, we have but very imperfect
and incomplete ideas of. Distinct ideas of the several sorts of bodies
that fall under the examination of our senses perhaps we may have: but
adequate ideas, I suspect, we have not of any one amongst them. And
though the former of these will serve us for common use and discourse,
yet whilst we want the latter, we are not capable of scientifical
knowledge; nor shall ever be able to discover general, instructive,
unquestionable truths concerning them. CERTAINTY and DEMO