Routledge History of Philosophy Volume IV

258 RENAISSANCE AND SEVENTEENTH-CENTURY RATIONALISM
Since the time of Hume, 25 many philosophers have taken the view that there is a
gap between questions of fact and questions of value, between ‘is’ and ‘ought’.
Philosophers who take a contrary view, and argue that human nature is relevant
to questions about the nature of what is morally good, are termed ‘naturalists’.
Spinoza is such a naturalist. He argued that if we are to discover the kind of life
that is good for a human being, we must discover the true nature of human
beings, and that this implies seeing ourselves in the context of nature as a whole.
Human beings, he says, 26 follow the universal laws of nature; the position of man
in nature is not that of a kingdom within a kingdom. One could summarize his
view by saying (adapting a phrase used by A.J.Ayer) 27 that man is a subject for
science. More will be said of Spinoza’s views about science and philosophy in
the course of this chapter, which is concerned with Spinoza’s metaphysics and
theory of knowledge (see especially pp. 287–9); his views about ethics and
politics will be discussed by Dr Blom in the next chapter.
In discussing Spinoza, I shall take as my primary source his Ethics. This is his
acknowledged masterpiece; a work of great range, covering not only moral
philosophy but also metaphysics and theory of knowledge, besides containing
the outlines of a system of physics and a theory of politics. The full title of the
book is Ethics, demonstrated in geometrical order, and indeed the most
immediately striking feature of the book is the geometrical order in which it is
presented. It is worth noting that, in presenting his philosophy in this form,
Spinoza is following a lead given by Descartes. The relevant topic here is
Descartes’s distinction between ‘analysis’ and ‘synthesis’, and although this has
already been discussed in a previous chapter, 28 it will not be superfluous to return
to it here. In Part II of his Discourse on Method, Descartes had written (CSM i,
120) that ‘Those long chains composed of very simple and easy reasonings,
which geometers customarily use to arrive at their most difficult demonstrations,
had given me occasion to suppose that all the things which can fall under human
knowledge are interconnected in the same way.’ This might lead one to expect
that Descartes would present his philosophy in geometrical form, and indeed in
the Second Set of Objections to Descartes’s Meditations Mersenne suggested
that this would be a worthwhile undertaking (CSM ii, 92). Descartes’s reply
turns on that distinction between analysis and synthesis which has just been
mentioned. The distinction goes back to classical Greek mathematics, and there
is a famous account of it in the writings of Pappus (fourth century AD), which
Descartes is known to have studied. Pappus states 29 that
In analysis, we assume as a fact that which we seek [to prove] and we
consider what arises out of this assumption; then we consider what that
follows from, and so on until, proceeding in this way, we come upon
something which is already known, or is one of our principles.
In short, in analysis we proceed back from what has to be proved to first
principles (Descartes calls them ‘primary notions’: Reply to Second Objections,