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A brief biography of Spinoza
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In common with most other early modern philosophers, Spinoza believed that scholastic logic was sterile, and incapable of yielding new truths. Again in common with the rest, he believed that the only example of a perfectly deductive science which yielded new and necessary truths, was Euclid’s geometry. But there the resemblance ends.

We have seen how Bacon thought that philosophy and science could be set on a sure footing, only by starting again with a reformed inductive method. He was less impressed by mathematics than Galileo, Descartes, and Hobbes, and he didn’t believe that the only properties of matter were quantitative (geometrical and mechanical).

Despite his writings on method, when it came to the crunch, Descartes held that knowledge is not gained by a method of reasoning at all, but by a clear and distinct perception of innate ideas — it’s the ideas themselves that count, rather than how you string them together.

Hobbes borrowed from Euclid (and, one might add, Socrates) the principle that you must start out from definitions, and stick rigidly to those definitions. But, unlike Euclid, he held that they were all you needed, and that valid reasoning was basically syllogistic (as for the scholastics). Nevertheless, he did have the interesting and original idea that syllogistic reasoning was identical with arithmetical reasoning, through the addition or subtraction of the components of definitions.

Spinoza’s new idea was to apply a strictly Euclidean method to philosophy and science, on the principle that if it works for geometry, why shouldn’t it work for everything else? Although (as you will discover) there are disadvantages to this method, Spinoza was by no means the last major thinker to adopt it. Newton’s Philosophiae Naturalis Principia Mathematica (1687) was laid out in exactly the same way; and in more recent times, Russell and Whitehead’s Principia Mathematica (1910–13) imitated Newton’s method as well as his title. Again, Wittgenstein’s Tractatus Logico-Philosophicus (1921), while not laid out in exactly the same way, is very much a homage to Spinoza, and reflects the title of Spinoza’s other great work, the Tractatus Theologico-Politicus. (It was an odd fashion to give Latin titles to vernacular works; there is also G.E. Moore’s Principia Ethica of 1903. But Hobbes’s had done it too: both his De Cive and his Decameron Physiologicum were in English.)

So what is the Euclidean method? The best way to see what it is like is to look at an example. Here are some extracts from the beginning of Book I of Euclid’s Elements, with my explanations in italics.

Go to Euclid’s Elements

Spinoza’s first attempt at writing philosophy using the geometrical method was his rewriting of the first two books of Descartes’ Principles of Philosophy, in the form of definitions, axioms, and propositions. It was probably quite a useful exercise, since it helped him to articulate the most important differences between Descartes’ system and his own. It was immediately afterwards that he set to work expounding his own philosophy in the same way.

Reading Spinoza’s Ethics is mostly rather slow-going, but rewarding. It is certainly nothing like as difficult (or unrewarding) as the following prize-winning entry to a recent competition on bad philosophical writing:

Go to Leahy

In my view, it would be barely reasonable to expect anyone to read the whole of the Ethics thoroughly even for a whole 10-credit module. You will be doing just Book I (which is less then one-fifth of the work) for about one-third of the module, and I shall still let you skip some of the less important passages. The main topics you will cover are God, matter, and determinism. But there’s a lot more to Spinoza’s philosophy than that, so I shall give you a brief summary, which will put what you do read into context.

But first a note on the title of the work, which may lead you to expect a treatise on ethics in the modern sense. ‘Ethics’ comes from the Greek word ethos meaning ‘custom’, and more specifically human customs, behaviour, and characteristics. To a contemporary readership (i.e. contemporary with Spinoza), it would convey much the same meaning as ‘A Treatise on Human Nature’. The word ‘moral’ has undergone a similar transition, only this time from the Latin mos (plural: mores) meaning ‘custom’. Add to this the fact that the words ‘philosophy’ and ‘science’ were used almost interchangeably until the 19th century, we have the explanation of why my philosophy degree from the University of Cambridge is a degree in ‘Moral Science’. It is contrasted with ‘natural science’ or ‘natural philosophy’, and is concerned with specifically human topics, such as human reasoning (logic), the foundations of knowledge (epistemology), knowledge which is presupposed by natural science (metaphysics), psychology, the relation between humans and God, and how people ought to behave, both individually and in society (ethics in the modern sense, and political philosophy). These topics map very closely onto the contents of Spinoza’s Ethics.

Nevertheless, it remains true that the Ethics has a profound moral purpose in the modern sense, and the culmination of the work is a discussion of what the good life consists in, given Spinoza’s metaphysics. Some might even claim that the nobility of the moral conclusion is an argument in favour of the metaphysics. Indeed, Kant was later to claim that the only possible ground for a metaphysical system is a moral one.