Routledge History of Philosophy Volume IV

RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM 365
according to Leibniz, there is only one kind of basic entities, namely souls. In
this respect the contrast with Spinoza’s monism is at a maximum. Far from
asserting that there is just one substance, Leibniz holds that there are infinitely
many simple substances and that, by virtue of the identity of indiscernibles, no
two are exactly alike.
Monads are in fact hierarchically arranged. At the top of the hierarchy is God
who seems to be the supreme monad; 45 at the bottom of the hierarchy are what
Leibniz calls ‘bare monads’ which provide the metaphysical foundation for
inanimate matter. The basis for this hierarchical classification is quality of
perception; borrowing Cartesian terminology, Leibniz says that monads differ in
terms of the clarity and distinctness of their perceptions. For example, the minds
of human beings are near the top of the hierarchy by virtue of their capacity for a
very high grade of perception, namely reason. A striking feature of monadology,
however, is that although monads differ enormously in terms of the quality of
perception, in a sense they do not differ in terms of the objects they perceive; for
giving a new twist to his expression thesis Leibniz holds that every monad
perceives the whole universe according to its point of view. The qualification
tacked on to this thesis is to be understood in terms of the doctrine that there are
qualitative differences among perceptions. To say that two monads differ in their
point of view is to say that they do not enjoy exactly the same distribution of
clarity and distinctness over their perceptual states. In this way Leibniz can also
explain how the identity of indiscernibles applies to monads in spite of the fact
that they all perceive the whole universe.
These are remarkable doctrines, and we may well wonder how Leibniz came
to arrive at them. In fact, however, the basic argument for the fundamental
principles of monadology is quite straightforward; it turns on two main
assumptions: the infinite divisibility of matter and the thesis that there must be
basic or ultimate entities. For Leibniz, it would be shocking to reason, or at least
to divine wisdom, if everything in the universe were composed of compounds
whose components were themselves compounds, and so on ad infinitum. The
infinite divisibility of matter implies that these basic entities cannot be physical,
for everything physical is a compound of the sort just described. Thus although
physical atoms are a fiction, there can and must be ‘spiritual atoms’ or monads.
A natural initial reaction to monadology is to wonder at Leibniz’s willingness
to prefer it to the more down-to-earth metaphysics of the Discourse. But in
response to the argument outlined above we may wonder why Leibniz was not in
a position to advance it earlier. Certainly throughout his career Leibniz holds that
the universe must consist of basic or ultimate entities. Moreover, in his earlier
philosophy Leibniz also held a version of the thesis of the infinite divisibility of
matter; matter, considered in abstraction from souls or substantial forms, is
infinitely divisible ‘in innumerable possible ways but not actually divided in
any’. 46 So at the time of writing the Discourse Leibniz believed, as he continued
to believe, that nothing purely material could be a basic entity. But the difference
between Leibniz’s earlier and later views seems to be this. In the Discourse