Routledge History of Philosophy Volume IV

266 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
distinctly understood without the other (Principles of Philosophy, Pt I, 60; CSM
i, 213). A mode, on the other hand, cannot be understood apart from the
substance of which it is a mode. ‘Thus there is a modal distinction between shape
or motion and the corporeal substance in which they inhere; and similarly, there
is a modal distinction between affirmation or recollection and the mind’ (ibid., Pt
I, 61; CSM i, 213). Although Spinoza rejects the idea that there can be a real
distinction between substances, he accepts the distinction between a mode and
that of which it is a mode, the only difference from Descartes being that
Spinoza’s modes are modes of the one substance, or of its attributes. He is saying
in effect that when we talk about particular things, then (even though there is in a
sense only one being, God) we are not indulging in mere fantasy. What would be
a mistake, and a serious one, would be to regard as independent substances what
are in fact modes of the one substance.
What makes Spinoza’s concept of a mode more than just a terminological
exercise is the use to which he puts it. It will be convenient to begin by
considering his views about the modes of the attribute of extension, where the
line of thought is easier to follow. In the first definition of Part II of the Ethics,
Spinoza explains that by a ‘body’ he understands a mode of the attribute of
extension. (This, incidentally, is a good example of his use of definitions. By
calling a body a ‘mode’, he claims, we understand what a body really is.) A body,
then, is distinct from another body in that they are different modes of one and the
same attribute. To explain the precise way in which they differ, Spinoza inserts
in the Ethics, between the Scholium to Proposition 13 of Part II and the next
proposition (G ii, 97–102), a sketch of a theory of physics. He takes it as
axiomatic that all bodies either move or are at rest, and that each body moves
now more slowly and now more quickly. What differentiate bodies (Lemma 1)
are differences in respect of motion and rest, speed and slowness; and these are
modal differences. Spinoza singles out motion and rest for special mention,
saying that they follow from the absolute nature of the attribute of extension, and
exist for ever and infinitely. 57 This means in effect that motion and rest (which
scholars call an ‘immediate infinite mode’ of extension) are universally present
in matter, and are of fundamental importance for the physicist.
Spinoza goes on to say that those bodies which are differentiated only by
motion or rest, speed or slowness, may be called ‘most simple bodies’ (Axiom 2
after Lemma 3). These corpuscles are the basic building-blocks of Spinoza’s
system of physics; they correspond roughly to atoms, 58 with the difference that
Spinoza’s ‘most simple bodies’ are modes, not independent substances. The
most simple bodies combine to form groups (Definition after Lemma 3), and
each such group is called by Spinoza one body, or an ‘individual’. An individual
has a certain structure, and as long as that structure is preserved, we say that the
individual is the same. (This, incidentally, has a bearing on one of the two
problems of substance mentioned on p. 284—namely, the problem of what it is
that remains the same when change occurs). Individuals are of varying
complexity, culminating in an individual of infinite complexity—that is, the