Although the distance may appear considerable between metaphysics and
physics, yet an idea of their connection runs through the whole system
of Leibnitz. He founds this on the principle, employed long ago by
Archimedes, “that there must be a sufficient reason for every thing.”
Leibnitz inquires, why bodies are extended in length, breadth, and
thickness. He holds, that to discover the origin of extension, we must
come at something unextended, and without parts; in short, at existences
entirely simple; and he contends, that “things extended” could have had
no existence, but for “things entirely simple.”
The foundations of this system were, in effect, long since laid by
Pythagoras and his disciples. Traces of it are in Strato of Lampsacus,
who succeeded Theophrastus in the Lyceum; in Democritus; in Plato, and
those of his school; and in Sextus Empiricus, who has even furnished
entire arguments to Leibnitz for establishing “the necessity of seeking
for the reason of compound things, in those which never had external
existence.” Moderatus Gaditanus, in relation to the numbers of
Pythagoras, says, “Numbers are, so to speak, an assemblage of units, a
progressive multitude which arises from unity, and finds there its
ultimate cause.” And Hermias, expounding the doctrine of the
Pythagoreans, says, that, according to them, “the unit, or simple
essence, was the origin and principle of all things.”
Sextus Empiricus deems it unworthy of a philosopher to advance, that
what falls under the notice of our senses, could be the principle of all
things; for things sensible ought to be derived from what is not so.
Things compounded of other things cannot possibly be themselves a
principle; but what constitutes those things may. Those who affirm that
atoms, similar parts, particles, or those bodies which only are to be
apprehended by the intellect itself, are the primary elements of all
things, in one respect say true, in another not. In so far as they
acknowledge for principles, only such things as fall not under our
senses, they are right; but they are wrong in apprehending those to be
corporeal principles: for as those bodies which fall not under our
senses, precede those which do, they themselves are preceded also by
what is of another nature: and as the letters are not a discourse,
though they go into the composition of it, neither are the elements of
body, body: but since they must be either corporeal or incorporeal, it
follows, that they are incorporeal. To this end he argues, that “bodies
are composed of incorporeal principles, not to be comprehended but by
the mind itself.”
To the same effect, Scipio Aquilianus, treating of the opinion of
Alcmæon, the Pythagorean, concerning the principles of things, reduces
it to a syllogism. “What precedes body in the order of nature, is the
principle of body; number is such a thing; therefore number is the
principle of body. The second of these propositions is proved thus:--Of
two things, that is the first, which may be conceived independent of the
other, whilst that other cannot of it. Now number may be conceived
independently of body, but not body of number; wherefore number is
antecedent to body in the order of nature.”
Marcilius Ficinus imputes to Plato the same notion, and gives us the
substance of that philosopher’s thoughts. “The different species of all
sorts of compounds may be traced out to something which in itself is
uncompounded; as the boundaries of body to a point, which has no
boundary; numbers to a unit, which consists not of numbers; and elements
to what has nothing in it mixt or elementary.” Marcilius Ficinus
expresses the system in a few words. “Compounds are reducible into
things uncompounded, and these again into what is still more simple.”
One sees here those compounds of Leibnitz, which, when reduced to their
simple parts, terminate in the Deity for their cause and source.
Plotinus also affirms, that “there must be in bodies some principle, or
substratum, entirely different from any thing corporeal.”
These quotations accord with passages in Plutarch concerning Heraclitus.
There are passages in Stobæus, from Epicurus, Xenocrates, and Diodorus,
to a similar purport; and a remarkable one in _Hebrews_ xi. 3. “Through
faith we understand that the worlds were framed by the word of God, so
that _things which are seen were not made of things which do
appear_.”[318]
It every where appears that Leibnitz drew many of his notions from
Plato; and he defines his “monads,” just as Plato does his ideas, τα
ὁντπως ὁντα, “things really existing.” An erudite German says, “I am
assured by one of my friends, who was himself informed of it by a
learned Italian, who went to Hanover to satisfy an ardent desire he had
of being acquainted with Mr. Leibnitz, and spent three weeks with him,
that this great man, at parting, said to him: ‘Sir you have often been
so good as to insinuate, that you looked upon me as a man of some
knowledge. Now, sir, I’ll show you the sources whence I drew it all;’
and immediately taking him by the hand, led him into his study, showing
him all the books he had; which were Plato, Aristotle, Plutarch, Sextus
Empiricus, Euclid, Archimedes, Pliny, Seneca, and Cicero.”