On Bodies which mutually repel one another.
Writers who have discoursed on the forces of bodies which attract others
have also spoken about the powers of bodies which repel, but especially
those who have instituted classes for natural objects on the basis of
sympathy and antipathy. Wherefore it would seem necessary for us to speak
also about the mutual strife of bodies, so that published errors should not
creep further, and be received by all to the ruin of true philosophy. They
say that, just as like things attract for the sake of preservation, so
unlike and contrary things for the same purpose mutually repel and put one
another to flight. This is evident in the reaction of many things, but it
is most manifest in the case of plants and animals, which attract kindred
and familiar things, and in like manner reject foreign and unsuitable
things. But in other bodies there is not the same reason, so that when they
are separated, they should come together by mutually {113} attracting one
another. Animals take food (as everything which grows), and draw it into
their interior; they absorb the nourishment by certain parts and
instruments (through the action and operation of the _anima_). They enjoy
by natural instinct only the things set in front of them and near them, not
things placed afar off; and this without any alien force or motion.
Wherefore animals neither attract any bodies nor drive them away. Water
does not repel oil (as some think) because the oil floats on water; nor
does water repel mud, because the mud, if mixed in water, settles down in
time. This is a separation of unlike bodies or such as are not perfectly
mixed as respects the material; the separated bodies nevertheless remain
joined without any natural strife. Wherefore a muddy sediment settles
quietly on the bottom of vessels, and oil remains on the top of the water
and is not sent further away. A drop of water remains intact on a dry
surface, and is not expelled from the dry substance. Wrongly therefore do
those who discourse on these matters infer an antipathy (that is, the force
of repelling by contrary passions); for there is no repelling force in
them; and repulsion comes[193] from action, not from passion. But their
greek vocables please them too much. We, however, must inquire whether
there is any body which drives anything else further off without material
impetus, as a loadstone attracts. But a loadstone seems even to repel
loadstone. For the pole of one loadstone repels the pole of another, which
does not agree with it according to nature; by repelling, it turns it round
in an orbit so that they may exactly agree according to their nature. But
if a somewhat weak loadstone, floating freely on water, cannot readily be
turned round on account of impediments, the whole loadstone is repelled and
sent further away from the other. All electricks attract all things: they
never repel or propel anything at all[194]. As to what is related about
certain plants (as about the cucumber, which turns aside when oil is
applied to it), there is a material change from the vicinity, not a hidden
antipathy. But when they show a candle flame put against a cold solid
substance (as iron) turn away to the side, and allege antipathy as the
cause, they say nothing. The reason of this they will see clearer than the
day, when we discourse on what heat is[195]. But Fracastorio's opinion that
a loadstone can be found, which would drive iron away, on account of some
opposing principle lurking in the iron, is foolish.
* * * * *
{115} [Illustration]