Routledge History of Philosophy Volume IV

268 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
15 of Part II of the Ethics), just as to talk of the human body is to talk of
something complex. In the case of the mind, the basic units are again modes, but
modes of the attribute of thought. Spinoza calls these modes ‘ideas’. 62
In what he says about ‘ideas’, Spinoza is opposing Descartes. Descartes had
introduced his sense of the term in the third of the Meditations, in which he said
(CSM ii, 25) that ideas are those thoughts which are ‘as it were the images of
things…for example when I think of a man, or a chimera, or the sky, or an angel,
or God’. The force of the phrase ‘as it were’ is that one cannot have a genuine
mental picture of an angel or of God; however, it does seem that for Descartes an
idea is at any rate picture-like, and that it is an entity which the mind perceives,
as distinct from the activity of perceiving. So, for example, in his reply to the
third Objections, Descartes explains (CSM ii, 127) that the word ‘idea’ means
‘whatever is immediately perceived by the mind’. Spinoza, on the other hand,
insists that an idea is an activity. In his definition of an idea in Definition 3 of
Part II of the Ethics, he says that an idea is a ‘conception’ (conceptus) of the
mind, and adds that he prefers the term ‘conception’ to ‘perception’ because the
former term ‘seems to express an action of the mind’. It emerges later 63 that,
when Spinoza speaks of an action of the mind here, he means that to have an
idea of X is to think of X, in the sense of making a judgement about it, that is,
affirming or denying something of it. It may be added that in using the term
‘idea’ in this way Spinoza is not being innovative, but is taking up a suggestion
which Descartes had put aside. In the Preface to the Meditations (CSM ii, 7)
Descartes had said that the term ‘idea’ could be taken to mean an operation of
the intellect, but went on to say that this was not how he proposed to use the
word.
It emerges from what is said later in the Ethics that Spinoza has two chief
reasons for preferring his definition of the word ‘idea’. Briefly, these are as
follows: (i) Descartes’s sense of the term forms part of a mistaken theory of
judgement. Descartes believed that two faculties are involved, namely the
intellect and the will (Meditation IV; CSM ii, 39). Spinoza, on the other hand,
argues 64 that the two are the same. To think of something (i.e. to have an idea of
something) is to make a judgement about it; for example, to think of a winged horse
is to affirm wings of a horse, (ii) Descartes is unable to explain our knowledge of
the truth; for how can we know that a true idea agrees with that of which it is the
idea? 65
All this is intelligible as a criticism of Descartes, but Spinoza’s own views
raise a problem: namely, that of the way in which an idea, as a mode of thought,
is related to the attribute of thought. The problem springs from the infinity of the
attribute of thought. In what sense, one asks, can an idea which a particular
person has be called a mode of this infinite attribute? One might perhaps suggest
that (by analogy with the attribute of extension and its modes) Spinoza views the
attribute of thought as some kind of infinite mind-stuff; but it is not at all clear
what might be meant by such a stuff. It may be that some light is thrown on the
problem by Spinoza’s theory of truth, which is discussed on pp. 296–7. To