XXIX. I have always wondered, and do not yet cease to wonder, at seeing
modern philosophers attack scepticism as a physical error, and am much
astonished, to find them condemn it in that sense as an error, dangerous
to the dogmas of faith. Nor can I comprehend, how such a charge can
arise, otherwise, than from gross ignorance or malicious spite; unless it
is applied to some sceptic, who from explaining himself loosely, may have
given occasion for such an imputation.
XXX. The system of physical scepticism, asserts, that physical and
natural things, do not admit of demonstration or scientific certainty,
but that they are all matter of opinion; and consequently, that we should
not call natural philosophy a science, because strictly speaking it is
not one, but rather a habit, or acquired facility, of reasoning with
probability upon natural things. We shall understand science in this
place, in the sense which Aristotle and the schoolmen understand it,
who define it, _to be an evident knowledge of the effect by the cause_.
But in our definitions, we shall not exclude experimental certainty,
or certain knowledge, acquired by the experience we have had, and the
observations we have made, of physical matters; but we shall rather
maintain it, as the only method by which we can arrive at attaining
truth; although I doubt whether we shall ever attain by it, a discovery
of the internal, or intimate nature of things.
XXXI. Neither will we deny, that with respect to physical objects, many
propositions may be advanced or supported, which are deducible with
infallible certainty from metaphysical principles: as for example from
this, _the whole is greater than its part_, is evidently inferred, that
a man is bigger than his head; and from this, _being is the effect of
operation_, is inferred, that my father existed when he begot me. But
these, and other innumerable demonstrations of this sort, afford no
physical knowledge whatever; because they do not manifest in any degree,
either great or small, the nature of the very entities which are the
objects of them. Why do I say manifest the nature of the entities? They
do not even display to the understanding, a single truth, which may not
be comprehended without their help, by the most rustic man upon earth.
So that the syllogistical conclusions upon infallible truths, which the
school philosophers so much boast of, do nothing more, than explain
by circumlocution and in terms of art, the very things, which may be
immediately comprehended, and naturally explained, by any rational
man who never studied. Further, how can they call by the name of
demonstrations, things which demonstrate nothing? that is, they manifest
nothing, but what was manifest without their assistance. A logician will
say, thinking he says something to the purpose, that he knows by means
of the art of demonstration, that which he could not know artificially
without this aid. But I answer, that this artificial knowledge is
totally useless, because it neither manifests to me any one truth of
which I was before ignorant, nor does it illustrate to me with greater
clearness, the things I was before acquainted with; it being certain,
that it is as evident and clear to the rustic, and that he assents with
as much firmness, that the whole tree is bigger than one of its branches,
without the help of artificial logic, as I do, assisted with my whole
armory of syllogisms. If a learned person, should undertake to instruct a
man who walks well, and with a good grace, by explaining to him all the
laws of motion, to step scientifically; and also, by explaining to him
the number and use of the muscles, should teach him the application of
those laws to every member of his body concerned in that exercise; should
not we be apt to say, that besides his taking a very tedious one, he had
also taken a very needless trouble, it being certain, that his pupil,
after all this pains, would not walk a jot better, if so well as he did
before; the cases are similar.