asn't first perceived by the senses, it is also the case that sensation by itself explains nothing; the universe as a whole or necessary propositions simply cannot be described from senses. For such an exercise, one needs a mind: "But the knowledge of eternal and necessary truths is what distinguishes us from simple animals and furnishes us with reason and the sciences, by raising us to a knowledge of ourselves and of God" (634).
In "Monadology," Leibniz calls upon the mind's capacity for abstraction to examine the nature of reality, implying the nature of the very universe. He argues from the premise of a "simple substance" (631), which he calls the monad, by which he means a unitary reality that cannot be altered, added to, subtracted from, destroyed, or corrupted in any way. Leibniz argues against the possibility of pieces of monads, for monads are indivisible. When Leibniz says that "accidents cannot be detached, nor can they go about outside of substances as the sensible species of the Scholastics once did" (631), he is saying that extension, which is subject to change, cannot, logically speaking, be an attribute of substance. On the other hand, "monads must have some qualities, otherwise they would not even be beings. And if simple substances did not differ at all in their qualities, there would be no way of perceiving any change in things" (631).
Indeed, Leibniz insists on differences of substances, seeing reality as a plurality of realities, or "a multitude in the unity or in the simple" (631). Logically speaking, a thing/entity/unit is either one thing or not, either one t
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