A Short History of Modern Philosophy: From Descartes to Wittgenstein, Second Edition (8 page)

The
philosophes
and the figures of the literary Enlightenment, authors of literary masterpieces as diverse as Voltaire’s
Le Siècle de Louis XIV
and Diderot’s
Le Neveu de Rameau,
would not have existed but for the decades of Cartesian metaphysics which cleared the intellectual air for them. Nevertheless, they play an insignificant part in the history of philosophy, neither adding to nor subtracting from the metaphysical ideas which their urbane scepticism made it more agreeable to them to ridicule than to understand. No doubt it is a further tribute to Descartes that his method should transmute itself into so many literary forms. But the history of philosophy proceeded independently, returning to the legacy of Descartes with a spirit which he would have recognised, but which was not his own.

Benedict de (Baruch) Spinoza (1632-1677), like Descartes and Leibniz, was a philosopher immersed in mathematical and scientific investigation. The greatest single influence on his thought was Descartes; he corresponded with men of science, such as Oldenburg (secretary to the newly formed Royal Society) and Boyle, and became an acknowledged expert in the science of optics, making his living (according to some accounts) as a lens-grinder. He was educated at the Jewish College in Amsterdam, to which city his Jewish parents had come from Portugal to escape persecution. Excommunicated from the synagogue for his sceptical beliefs, he settled among a group of enlightened Christians, who had formed a philosophical circle of which he soon became the leader. Then, leaving Amsterdam, he lived a secluded unworldly existence, refused offers of money and academic distinctions, and even withheld his great
Ethics
from the press, as much from love of truth and intellectual independence as from any fear of the censor. He died of consumption, leaving his major work unpublished.

Spinoza’s philosophy rests on two principles. First, a rationalist theory of knowledge, according to which what is ‘adequately’ conceived is for that reason true; secondly, a notion of substance, inherited through Descartes from the Aristotelian tradition of which Descartes himself was the unwilling heir. From the standpoint of metaphysics it is perhaps Spinoza’s greatest distinction that he examined this notion of substance, and refused to let it go until he had extracted from it every particle of philosophical meaning.

Like Descartes, Spinoza sought for what is certain, and regarded the pursuit of certainty as providing the only guarantee of human knowledge. However, unlike Descartes, he did not seek to found his system in the single indubitable premise of the ‘cogito’. The proposition ‘I think’ has two features which rendered it useless to Spinoza. First, it expresses a merely contingent truth, whereas for Spinoza all certainty must ultimately be founded in necessities. Secondly, it contains an ineliminable reference to the first person, while for Spinoza access to philosophical truth comes only when we rise above preoccupation with our own limited experience and mentality, and learn to see things from the impartial point of view of the rational observer to whom things appear ‘under the aspect of eternity’
(sub specie aeternitatis).

The geometrical method

Spinoza took as his model of objective rational enquiry the geometry of Euclid. This, he believed, began from axioms, the truth of which could be seen to be necessary, and from definitions which clarified the concepts used to formulate them. Furthermore it advanced by indubitable logical steps to theorems which, by virtue of the deductive method, must be as certain and free from error as the axioms from which they were derived. In setting up the geometrical method as his philosophical ideal, Spinoza expressly laid aside ordinary conceptions and everyday language. He argued that his definitions were not arbitrary plays on words, but the instruments whereby certain antecedent ideas may be formulated in a language more precise than that made available by the vernacular.

One of the few works published in his lifetime was
The Principles of Cartesian Philosophy
(1663), in which he tried to lay down all the fundamental axioms to which Descartes’ metaphysics could be reduced, and then to deduce from those axioms the actual content of Descartes’ philosophy. The work is a brilliant summary, and of great interest in being written from outside the artificial standpoint of Descartes’
Meditations,
in which metaphysical doubt is cured only by the invocation of a highly specific contingent premise. But the principal exemplification of Spinoza’s geometric method is in the
Ethics,
where Spinoza’s own philosophy is set out in axiomatic form. Beginning from what he took to be correct definitions of notions indispensable to the description of reality, Spinoza attempted to prove not only propositions of a metaphysical system as ambitious as any since Plato, but also the precepts of rational conduct and the description of our moral and emotional nature. His system moves with equal geometrical rigour towards the proposition that ‘a substance is prior in nature to its modifications’ and towards the proposition that ‘there cannot be too much merriment, but it is always good; but on the other hand melancholy is always bad.’ (The proof of this second proposition involves, when traced back to original axioms, something like a hundred separate steps; it looks less inaccessible to rational thought when placed beside Spinoza’s view that merriment can be ‘more easily conceived than observed’.)

Substance

The Cartesian notion of substance, appealing though it was on logical, scientific and metaphysical grounds, gave rise to problems that steadily increased in significance as their depth was perceived. What is the relation between substance construed as individual and substance construed as matter or stuff? How many substances are there? How, if at all, can we explain their interaction? If they can sustain themselves in existence, why do we need an explanation of their origin? Descartes and the Cartesians gave various answers to those questions, none of them felt to be satisfactory. Spinoza was quick to observe that the concept of substance is, nevertheless, the cornerstone of Cartesian metaphysics. Hence each of those questions must be answered unequivocally and consistently if the metaphysical structure is to stand up to philosophical examination. If metaphysics collapses, then, Spinoza believed (and in this he was at one with all rationalist thinkers), so does the possibility of science.

In the
Principles
Descartes had touched on the problems posed by the concept of substance and made a distinction between the ‘principal attribute’ of a substance (the attribute which constitutes its nature, as extension is the nature of physical things and thought the nature of mind) and its ‘modifications’ or ‘modes’—the properties in respect of which it can change without ceasing to be what it is. He also noted an ambiguity in the term ‘substance’, which might be used in a wide sense, to denote any individual object, or in a restricted sense, to refer to that which depends upon nothing outside itself for its existence. In this restricted sense, he argued, only God is a substance.

It is this restricted idea of substance that provides the cornerstone of Spinoza’s metaphysics. A substance, he writes, is ‘in itself and conceived through itself’, or is ‘that the conception of which does not depend upon the conception of another thing from which it must be formed’. A substance must be intelligible apart from all relations with other things. Hence a substance cannot enter into relations and, in particular, can be neither the cause nor the effect of anything outside itself. To the extent that a thing is caused, it must be explained in terms of, and therefore ‘conceived through’, other things. A substance therefore cannot be produced by anything else: it is its own cause
(causa sui
)—which means, according to Spinoza’s definition, that its essence involves existence.

Spinoza, evidently influenced by Descartes, distinguishes the attributes of a substance from its modes. An attribute is that which ‘the intellect perceives as constituting the essence of a substance’, whereas a mode is that which is ‘in something else’ through which it must be conceived. The word ‘in’ here creates difficulties, but here is an analogy: a group of people join to form a club which then does things, owns things, organises things. When I say that the club bought a house, I really mean that the members of the club did various things, with a specific legal result. But none of the members bought a house. Hence it looks as though the club is an independent entity, existing over and above the people who compose it. In fact, however, it is entirely dependent for its existence and nature on the activities of its members. The club is ‘in’ the members, in Spinoza’s sense. And when
x
is ‘in’
y, x
can be understood fully only
through y.
Another way to put the point is:
y
is ‘prior to’ x, since we cannot understand x without a prior conception of
y.
In this sense, ‘a substance is prior in nature to its modes’.

The first part of the
Ethics
is devoted to God, defined as ‘a substance consisting of infinite attributes, each one of which expresses an eternal and infinite essence’. Spinoza follows Descartes in giving a version of the ontological argument. However, the proof has an interesting twist to it. Spinoza believes that all substances exist necessarily, since ‘it belongs to the nature of substance to exist’. But he also argues that ‘there cannot be two or more substances with the same nature or attribute’; in other words, substances cannot share attributes. Since God possesses all attributes, therefore, there can be no other substance besides God. Everything that exists is ‘in’ God.

God has ‘infinite attributes’. Extension is an attribute, since we perceive it as constituting the essence of the corporeal world: there is nothing more basic than extension to which the explanation of corporeal things could be referred. We have full (or, as Spinoza puts it, ‘adequate’) knowledge of the nature of extension through the science of geometry, and the existence of this systematic science of necessary truths is further proof that the idea of extension delivers God’s essential nature to our intellect.

Monism

Extension is an attribute of God, and like all the attributes of God it is infinite in quantity (which means, to put it crudely, that space has no boundaries, a proposition for which Spinoza provides an independent proof). It remains to examine what other attributes God might have. The other candidate bequeathed by Cartesian philosophy was thought, which Descartes put forward as the essential characteristic of mind. Spinoza argued that this too must be an attribute of the single divine substance, since it can be conceived in itself and there is nothing beyond itself by reference to which we must conceive or explain it. It has modifications— specific thoughts, images and agglomerations of the same—just as extension has its modifications. But in the rational explanation of these it is to thought alone that we need refer; having referred to thought, we do not need to go beyond it to some more basic attribute through which thought itself must be conceived. This explains why the properties of thought are pellucid to us (although it is clear on reflection that thought and extension are pellucid in a different way and for different reasons). Thought, therefore, is another attribute of the divine substance.

While there are of necessity infinitely many such attributes, to finite beings only finite knowledge is available. Thus we can conceive God through the attribute of extension and through that of thought, while other manners of conception lie outside our intellectual capacity. In so far as the world is knowable to us, therefore, it consists of one thing, seen under two aspects, which correspond to its two knowable attributes. It can be seen either under the aspect of thought, in which case we call it God, or under that of extension, in which case we call it Nature. God or Nature
(Deus sive Natura)
is the single existing thing which exists of necessity and, being cause of itself, persists through all eternity. Thought and extension are not mere properties of God: they each constitute God’s essence, and each therefore present to the intellect a full and adequate idea of what God is.

It is of course extremely puzzling to imagine in this way
one
thing with more than one essence: the concept of an ‘attribute’ only seems intelligible when construed epistemologically, as a reference to the two possible ways of knowing God; the alternative, ontological, conception, which attributes two separate essences to God, is extremely difficult to understand. But Spinoza definitely meant us to construe his theory ontologically, believing that only then will the full intellectual consequences contained in the concept of substance be understood. Only then could it be seen that the very same ontological argument that shows the existence of a substance, explains also the existence of thought and of extended matter. There ceases to be a distinction between creation and the creator, and the greatest theological problem therefore dissolves. Likewise there ceases to be a real distinction between mind and matter: so the greatest metaphysical problem also dissolves. Mind, matter, creation, creator—all these are simply names of the same eternal self-sustaining thing.

Mind and its place in nature

The theory of the attributes was partly intended by Spinoza to solve an outstanding question raised by Descartes’ philosophy of mind. If the mind is, or belongs to, a separate substance from that of the body, then how do mind and body interact? What mechanism can join two substances, so that changes in the one are explained by changes in the other? On Spinoza’s reading of ‘substance’ the suggestion is a nonsense, and his reading, he thought, is the only consistent one.

Spinoza’s solution to the problem of mind and body is ingenious, although hard to understand in its entirety. The mind and the body are one and the same thing, which is conceived now under the attribute of thought, now under the attribute of extension.’ The theory of the attributes implies not only that the one substance can be known in two ways, but that the same two ways of knowing apply also to the modes of that substance. The mind is a finite mode of the infinite substance conceived as thought; the body is a finite mode of the infinite substance conceived as extension—and these two finite modes are in fact one and the same. Spinoza summarises the theory by saying that the mind is the idea of the body.