XII. The school philosophers call all those qualities occult, which are
not reckoned among the four elemental ones, and which do not result
from the various combinations of these elemental ones, because they
suppose their operations move in a line superior to those which may
be supposed to proceed from humidity, dryness, cold, heat, hardness,
softness, colour, favour, &c. And although it is true, that some by
pursuing the system of assigning second qualities, which result from the
various combinations of the first; or third qualities, resulting from the
various combinations of the second; and among these third, have placed
the wonderful virtues of the load-stone, the operation of purges, and
others of those which they call occult, and which by these means they
have attempted to reduce to manifest ones; this mode of proceeding, has
been abandoned by the generality of philosophers, and with reason; for
it is very clear, that combine, and recombine, the qualities of humidity,
dryness, heat, and cold, in what way you will, you will not be able to
find out, that they are capable of directing the load-stone to the Pole,
or of causing it to attract iron.
XIII. It is not my intention, to examine the nature and origin of all, or
either of these qualities; but shall only say, that they are all equally
occult, or are all equally manifest. In order to demonstrate this, we
will compare the calefactive virtue of fire which is looked upon as the
most manifest, with the attractive virtue of the load-stone, which is
reputed the most occult. All that is known, or that is taught by the
peripatetic doctrine, of the calefactory virtues of fire, may be reduced
to this, that it is a property appertaining to that substance, or a
quality that springs from, or arises out of its form, that produces the
effect which we call heat, and that the action with which it causes it,
is called calefaction; but so it is, that it is just in the same manner
that we know the attractive virtue of the load-stone; _viz._ that it is a
property or quality, springing from, or arising out of the form of this
entity, that produces the sensible effect of drawing the iron to it, and
that the action with which it causes it to approach towards it, is called
attraction; it follows then, that we know just as much of the attractive
virtue of the load-stone, as we know of the calefactory virtues of fire;
and therefore, both of them are equally occult, and equally manifest.
XIV. And if we were to speak the truth, how could we deny, that the
quality we call heat is occult, when it is even occult, whether it is
or is not a quality? Not only the corpuscular philosophers deny it to
be possessed of all quality or form, but many of those who admit those
properties to be contained in it, constitute the heat to proceed from a
vertical, or vibratory motion of the insensible particles of the body.
And so long as we shall remain without an argument to convince us of the
truth of these opinions, we shall not know which of them is right.