Routledge History of Philosophy Volume IV

RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM 375
which requires that any two minds must be qualitatively, not just numerically,
different. Although Leibniz is not quite explicit about this, another assumption of
the argument seems to be that minds at or before birth have no conscious
experiences; thus the individuating characteristics required by the identity of
indiscernibles must occur below the threshold of consciousness. 82 Other
arguments are less tied to the distinctive principles of Leibniz’s metaphysics, but
not all of them are more cogent. Leibniz is fond of arguing that, in order to hear
the waves breaking on the shore, we must hear the noise of each individual
wave. 83 This argument has been criticized as being as dubious as arguing, from
the fact that we feel the weight of a stone, that we must have an unconscious
perception of each of the molecules that make it up. 84
Perhaps more interesting is what we may call Leibniz’s ‘attention argument’
which may be illustrated by the following scenario. 85 Suppose that two people,
Smith and Jones, are having a conversation and that, throughout, a drill has been
operating in the background; Smith has not been conscious of the noise, but he
now suddenly has his attention drawn to it by Jones. Leibniz argues that in the act
of attention Smith is really remembering a past perception of the noise. But ex
hypothesi this earlier perception was not a conscious one and must therefore have
been ‘little’ or unconscious. This argument clearly depends on the premise that
attention involves memory, and one might wonder why one should accept this. If
it is supposed to be true by definition, then the definition seems merely
stipulative. Nonetheless, there is something attractive about the suggestion that
cases like this force us to recognize the existence of unconscious perceptions,
and Leibniz can support his conclusion in other ways. For example, it was
implicitly assumed in our description of the case that Smith’s sense organs are
equally stimulated by the drilling both before and during the act of attention.
Now Leibniz cannot of course strictly ascribe any psychological effects to a
physical stimulus, but by virtue of his theory of expression he can and does insist
that some state of the soul must correspond to any such stimulation; 86 and by
hypothesis, as we have seen, the mental state which precedes the act of attention
is not a conscious awareness of the noise. Leibniz can also fall back on an appeal
to the law of continuity; 87 there would be a flagrant breach of this law if the
stimulus which ‘produced’ a conscious perception of the noise during the act of
attention ‘produced’ no perception at all in the mind before the act.
The doctrine of unconscious perceptions is a key element in Leibniz’s attack
on the Cartesian view that mentality is all or nothing. For Leibniz, by contrast,
mentality is a continuum which extends below the threshold of consciousness.
Sometimes, as we should expect, Leibniz’s rejection of Descartes’s view of the
mental life provides the basis for the rejection of other Cartesian doctrines.
Leibniz sides with common sense against the notorious Cartesian thesis that
animals are mere automata. He argues that the Cartesians were led astray by their
failure to distinguish between thought and perception; in other words, the
Cartesians have made the mistake of confusing a species with its corresponding
genus. 88 Thus even if animals have no thought (cogitatio), it does not follow that