Routledge History of Philosophy Volume IV

RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM 367
that bodies are sets of harmonized perceptions. 48 Leibniz seems to have flirted
with this thesis on occasion; in a very Berkeleian passage he tells Des Bosses:
It is true that things which happen in the soul must agree with those which
happen outside of it. But for this it is enough for the things taking place in
one soul to correspond with each other as well as with those happening in
any other soul, and it is not necessary to assume anything outside of all souls
or monads. According to this hypothesis, we mean nothing else when
we say that Socrates is sitting down than that what we understand by
‘Socrates’ and by ‘sitting down’ is appearing to us and to others who are
concerned. 49
Leibniz was certainly well placed to defend a version of phenomenalism. Other
phenomenalists, such as Berkeley, who hold that the supply of souls or minds is
finite are forced to analyse statements about the existence of physical objects in
terms of statements about possible perceptions; they are forced to appeal to the
perceptions which a mind would have in such and such circumstances. Leibniz,
by contrast, does not have to take this line since he holds that the number of
souls is infinite and that every possible point of view on the phenomena is
actually occupied. Thus Leibniz can analyse all statements about the existence of
physical objects in terms of other statements which are exclusively about the
actual perceptions of monads. 50
Phenomenalism, however, does not seem to be Leibniz’s considered view. Most
characteristically Leibniz states that a physical object is, not a set of perceptions,
but an aggregate of monads or simple substances. In saying this Leibniz is careful
to point out that he does not mean that monads are parts of bodies; rather, any
part of a body is itself physical, and since matter is infinitely divisible, there will
be no part of matter which does not have parts which are themselves smaller
bodies. Leibniz sometimes explains the relationship between bodies and monads
by saying that bodies are ‘beings by aggregation’ which result from monads or
simple substances. 51 Bodies are also said to be ‘well-founded phenomena’; 52 they
are well-founded in the sense that they are appearances which are grounded in
monads.
Despite some differences in formulation, Leibniz’s main view seems to be that
bodies are aggregates of monads. We may well wonder how this can be so; how
can an aggregate of simple, unextended substances be identified with a physical
object? It would seem that a physical object must have properties which no
aggregate of monads could have. Certainly a physical object must have
properties which no individual monad can have. Perhaps Leibniz would insist on
the logical point that, from the fact that individual monads are unextended, it does
not follow that an aggregate of monads is unextended; to suppose otherwise is to
commit the fallacy of composition. This fits in well with Leibniz’s claim that
‘aggregates themselves are nothing but phenomena, since things other than the
monads making them up are added by perception alone by virtue of the very fact