Routledge History of Philosophy Volume IV

274 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
something perfectly or in the best way’. When Spinoza says in the Ethics,
therefore, that a person who has a true idea knows that he has a true idea, he is
not saying something that is inconsistent with what Plato had said about
knowledge and true belief; what he is saying is that the person who knows, knows
that he knows.
There is more to be said about Spinoza’s views concerning knowledge and
truth. In the note to Proposition 43 of Part II of the Ethics that has just been
cited, Spinoza says, not just that to have a true idea is to know, but that it is to
know something ‘perfectly or in the best way’ (perfecte sive optime). Here, he is
referring to a point already made in Part II of the Ethics (Note 2 to Proposition
40)—namely, that there are various kinds of knowledge. 77 Now, from what he
says about these kinds of knowledge it emerges that it is possible to have
knowledge of a sort—knowledge which is not perfect—without having a true
idea, in that the idea that one has is only inadequate. The suggestion that one can
know that p, even though the proposition that p is not true, may seem to be yet
another paradox. However, a consideration of what Spinoza has to say about the
kinds of knowledge shows that the paradox is only apparent.
In the note just mentioned, Spinoza says that there are three kinds of
knowledge, which he calls respectively ‘imagination’, ‘reason’ and ‘intuitive
knowledge’. The first of these is the one that is relevant to the topic now at issue,
and will concern us in the rest of this section. ‘Imagination’ includes particular
propositions that are based on sense experience and general propositions which are
derived by induction from particular instances. 78 Spinoza says that such
knowledge is knowledge from what one may render as ‘uncertain’ or
‘inconstant’ (vaga) experience. By this he means (ibid.) that the ideas involved
are fragmentary and without rational order; he also says that they are ‘inadequate
and confused’ (Proposition 41 of Part II). This means, then, that there is a kind of
knowledge—namely, imagination—which involves inadequate or false ideas.
Light is thrown on this by Spinoza’s remark (Ethics, Pt II, Proposition 28) that
confused ideas are ‘like consequences without premises’. What Spinoza means
may be explained as follows. Suppose that I see a certain pen in front of me;
suppose, too, that there really is a pen there—i.e. no sense illusion is involved.
Now, my seeing this pen is the result of a complex set of causes; but in so far as I
merely see the pen, I am unable to trace these causes. That is, I am unable to give
an explanation of what it is for me to see this pen. So although I know that there
is a pen there (more of this later) I have only an inadequate idea of the pen. If I
am to have an adequate idea of it, I must make use of knowledge which does not
rest on sense experience alone. For example, I must make use of physics, to
explain the relation between the pen and my sense organs and brain, and I must also
make use of metaphysics, to explain the relation between a corporeal state and
the corresponding idea.
Another sort of imagination recognized by Spinoza is knowledge based on
induction. His account of this is very brief but appears to proceed along lines that
are similar to his account of sense experience. Just as there is knowledge that