Routledge History of Philosophy Volume IV

376 LEIBNIZ: TRUTH, KNOWLEDGE AND METAPHYSICS
they have no perceptions. Leibniz is clear, then, that animals have a mental life,
but he is less clear about its precise nature. He seems to have believed that,
unlike humans, animals have no capacity for self-consciousness, but whether he
believed that they could consciously feel pain is less certain. Unfortunately, the
issue is complicated by an obscurity in Leibniz’s concept of apperception which,
as we have suggested, is ambiguous between consciousness and selfconsciousness.
89
Somewhat curiously, however, at other times Leibniz uses his theory of
perception to defend Cartesian theses, although often in a seriously modified
form. Here too the doctrine of unconscious perceptions plays a key role. As
against Locke, for example, Leibniz exploits the doctrine in order to defend, or
rather re-work, the Cartesian thesis that the mind always thinks. For Leibniz, the
mind always thinks, not in the sense of being always conscious, but rather in the
sense of never being without some perceptions; for example, even in dreamless
sleep or a coma the mind has its petites perceptions. It is thoroughly
characteristic of Leibniz’s concerns that his defence of this Cartesian thesis is in
the service of a larger goal—the vindication of an immaterialist theory of mind
against what he sees as Locke’s subversive attack on this doctrine. For Leibniz,
the immateriality of the mind entails that it is naturally immortal, and this in turn
entails that it always perceives. 90
KNOWLEDGE AND IDEAS
In contrast with Locke and the other British empiricists, Leibniz has traditionally
been classified as a rationalist, and this classification is fundamentally an
epistemological one: a rationalist philosopher is one who believes that it is
possible to know substantive truths about the world a priori, by reason alone. We
might expect, then, that in his full-length reply to Locke, the New Essays,
Leibniz would seize the opportunity to provide a systematic defence of the
rationalist position in epistemology. Yet on the whole this expectation is
disappointed. On the contrary, as I have already indicated, Leibniz’s main
purpose in this work is not epistemological at all: it is metaphysical. Leibniz told
a correspondent that in writing this work he was above all concerned to defend
the immateriality of the soul. 91
This fact about the work is remarkably suggestive of Leibniz’s overall
philosophical orientation. Unlike Descartes and the British empiricists, Leibniz
was not greatly interested in what have since come to be regarded as the central
issues in epistemology; the problem of our knowledge of the external world, for
instance, was never at the forefront of his philosophical concerns. As we have
seen, Leibniz sometimes toys with phenomenalism, and in the hands of Berkeley
phenomenalism serves as an answer to the challenge of scepticism. Leibniz,
however, does not seem to have been primarily attracted to phenomenalism for
this reason. On occasion, of course, Leibniz can make some shrewd criticisms of
the attempts of other philosophers to solve epistemological questions. Leibniz is