
D’Holbach,
The System of Nature
19
which, to our eyes, appear to enjoy the most perfect repose, are nevertheless decomposed and
dissolved in the course of time. The hardest stones, by degrees, give way to the contact of air.
A mass of iron, which time, and the action of the atmosphere, has gnawed into rust, must
have been in motion from the moment of its formation in the bowels of the earth, until the
instant we behold it in this state of dissolution.
Natural philosophers, for the most part, seem not to have sufficiently reflected on what they
call the
nisus;
that is to say, the incessant efforts one body is making on another, but which,
notwithstanding, appear, to our superficial observation, to enjoy the most perfect repose. A
stone of five hundred weight seems at rest on the earth, nevertheless, it never ceases for an
instant to press with force upon the earth, which resists or repulses it in its turn. Will the
assertion be ventured, that the stone and the earth do not act? Do they wish to be undeceived?
They have nothing to do, but interpose their hand betwixt the earth and the stone; it will then
be discovered, that, notwithstanding its seeming repose, the stone has power adequate to
bruise it. Action cannot exist in bodies without re-action. A body that experiences an impulse,
an attraction, or a pressure of any kind, if it resists, clearly demonstrates by such resistance,
that it reacts; from whence it follows, there is a concealed force, called by philosophers
vis
inertia,
that displays itself against another force; and this clearly demonstrates, that this inert
force is capable of both acting and re-acting. In short, it will be found, on close investigation,
that those powers which are called
dead,
and those which are termed
live
or
moving,
are
powers of the same species, which only display themselves after a different manner.
6
May we not go farther yet, may we not say, that in those bodies, or masses, of which the
whole appears to us to be at rest, there is, notwithstanding, a continual action and reaction,
constant efforts, uninterrupted impulse, and continued resistance? In short, a
nisus,
by which
the component particles of these bodies press one upon another, reciprocally resisting each
other, acting, and reacting incessantly?
that this reciprocity of action, this simultaneous
reaction, keeps them united, causes their particles to form a mass, a body, a combination,
which, viewed in its whole, has the semblance of complete rest, although no one of its
particles ever
really
ceases to be in motion for a single instant? These bodies appear to be
at rest, simply by the equality of the motion of the powers acting in them.
Thus bodies that have the appearance of enjoying the most perfect repose, really receive,
whether upon their surface, or in their interior, continual impulsion from those bodies by
which they are either surrounded or penetrated, dilated or contracted, rarefied or condensed;
in short, from those which compose them: whereby their particles are constantly acting, and
reacting, or in continual motion, the effects of which are ulteriorly displayed by very
remarkable changes. Thus heat rarefies and dilates metals, which clearly demonstrates, that
a bar of iron, from the variation of the atmosphere alone, must be in unceasing motion; and
that not a single particle in it can be said to enjoy rest, even for a single moment. Indeed, in
those hard bodies, the particles of which are contiguous, which are closely united, how is it
possible to conceive, that air, cold or heat, can act upon one of these particles, even
exteriorly, without the motion being successively communicated to those which are most