There are two further respects in which the Port-Royal logic deserves recognition. First, because of its quasi-mathematical development of part of the medieval logic. This development must have seemed natural to any follower of Descartes, but it contained the first premonition of modern formal logic. Secondly, because of its distinction, again novel at the time but now considered fundamental to logic, between the ‘comprehension’ and ‘extension’ of a general term. The word ‘comprehension’ denotes that which is understood in understanding a term—in other words, the idea that the term expresses. The extension of a term, on the other hand, is the set of things to which it is applied. (Thus the comprehension of the term ‘man’ is the idea of manhood, its extension is the class of men.) Following the nineteenth-century Scottish philosopher Sir William Hamilton, the distinction is now often expressed as that between the intension and the extension of a term. It was important to Arnauld and Nicole, since they wished to isolate the former (the realm of ‘ideas’) as giving the true subject matter of logic; it is important in modern thought for the opposite reason, because logicians have come increasingly to realise that logic is the science not of the intension, but of the extension of terms (see chapter 17).
The Port-Royal school projected a manual on mathematics, and, as a preface to this, Blaise Pascal (1623-1662) wrote his De l’esprit géometrique, an investigation into the philosophy of mathematics designed to display not just the nature of the ‘geometrical’ method, but also its limits. Pascal, like Descartes, was a great mathematician and a deeply religious man. But his faith, which he acquired by conversion, took the passionate form characteristic of Jansenism, according to which the claims of reason could never suffice as foundations for so great a thing as religious doctrine. Pascal argued that the indefinability of terms and the need for axioms in the ‘geometrical method’ showed not the absolute validity of the ‘clear and distinct idea’, but rather the imperfection of finite minds, which must always rest content with indefinables. Our reason may give us some guarantee of the methods of the geometer, but it could never provide the same guarantee for his axioms.
In the famous Pensées (published posthumously) Pascal takes further his strictures on the use of reason, arguing that, since God is hidden from mortal view, it is futile to attempt to discover his essence through rational enquiry. ‘We know truth not only by reason but more by the heart.’ And it is from the heart that we sense the meaning of life and its divine eschatology. Pascal stopped short of total scepticism, believing it to be self-defeating, and qualified his strictures against rational theology with a curious argument for the existence of God: ‘Pascal’s wager’. The argument goes roughly as follows: ‘If God exists He will reward belief in Him: while if He does not exist, such belief leads to no harm. Hence the best bet is to believe in Him.’ The argument reflects Pascal’s concern with the concept of probability; it is interesting because it offers practical reasons (rather than theoretical reasons) for an article of faith, so connecting the logic of religious belief not with that of science but with that of practice. This singularly modern idea—which resurges periodically in later philosophy, for example in Kant’s conception of the ‘ideas’ of reason, in Kierkegaard’s notion of the ‘leap’ of faith, in the neo-Marxist theory of praxis and in the existentialist concept of commitment—possesses less philosophical merit than rhetorical impact.
For while it is indeed a striking suggestion that religious belief may be constituted by a form of voluntary activity, and so be inaccessible to metaphysical doubt, it seems hard to reconcile with the obvious fact that the question of the existence of God is a question about what is true, and not a question that could be resolved by mesmerising ourselves into a state of unfounded belief in Him.
Perhaps the greatest of the many philosophers who could reasonably be called Cartesian was Nicolas Malebranche (1638-1715), a priest of the Oratory who engaged in a vivid and at times bitter controversy with Arnauld over matters of theology and metaphysics. Like Pascal, Malebranche was distinguished by his literary gifts and produced—in his Dialogues on Metaphysics (Entretiens sur la métaphysique et sur la religion, 1688)—some of the finest philosophical prose since Plato. But he did not share Pascal’s distrust of metaphysics and conceded to mysticism only a narrow region of carefully circumscribed darkness. Malebranche had thoroughly absorbed the principles and proofs of the Cartesian philosophy, but, like many who were convinced that Descartes’ method was both valid and comprehensive, he remained unsatisfied with the Cartesian picture of the relation between body and soul.
Descartes’ views of causation are such that there is a prima facie contradiction between the thesis that body and soul are (or exemplify) separate substances, and the thesis that there is also interaction between them. Malebranche did not seek to question the Cartesian idea of substance, although his writings are remarkable for containing an extended metaphysics from which that idea could be eliminated without detriment to the system’s integrity. Instead, he questioned the theory of causation implicit in Descartes: the theory that the states of a substance must be explained in terms of its essential nature. It seemed to Malebranche that such a theory could explain neither our ability to perceive the material world, nor our ability to act on it. Furthermore (and in this he showed how much he had let the Cartesian conception of material substance fall into the background of his philosophy, replacing it with the more modern idea of the material object), he even regarded it as incompatible with the view that there is causal action between separate bodies, since it seemed to imply that each body, being complete in itself, had nothing to gain from or to impart to its surroundings. Rejecting the view that bodies have an intrinsic ‘power’ to affect us and each other as a mere superstition, Malebranche adopted the theory, already proposed by the Cartesians du Cordemoy (c. 16051684) and Arnold Geulincx (1624-1669), of ‘occasionalism’, which he defended with great vigour. This theory—perhaps the first developed account of the concept of causation in modern philosophy—argues that, since the laws of the universe have their origin in God, it is God who produces the events that conform to them. No event produces another of its own nature. Rather, when one thing occurs, then this is the occasion for God’s production of that thing which we know as its ‘effect’. In this view, there is no special difficulty posed by the relation between mind and body, since to speak of interaction between them can only be a manner of speaking: just as it is only a manner of speaking to refer to interaction between anything.
There is much more to Malebranche’s metaphysics than this theory (often wrongly thought to be, not a general philosophy of causation, but rather an ad hoc apologetic whereby to reconcile the Cartesian theory of mind with the obvious). In particular Malebranche upheld and developed the Cartesian theory of continuous creation; he supported the view that science must be rooted in a priori metaphysical principles; and he reaffirmed the distinction between the rationally conceivable essence and the empirically perceivable properties of things. But his influence in these matters was less great than it might have been. The Cartesian philosophy was already being eclipsed by the more systematic work of Spinoza and Leibniz, and by the powerful attack on rationalism initiated by Hobbes and given magisterial form in Locke’s Essay on the Human Understanding.
It is impossible to leave the subject of the Cartesian revolution without taking a brief forward glance into that intellectual movement known to the historian of ideas as the ‘Enlightenment’, and known to philosophers either as the eighteenth century, or as nothing at all. By the end of the seventeenth century, scientific knowledge, and the Cartesian clarity of expression, had become universal properties of the educated class; and a new literature began to arise, encyclopaedic in its aims, antiauthoritarian in its preconceptions and outspoken in its style (see especially Pierre Bayle (1647-1706): Dictionnaire historique et critique, 1696). Culminating in the writings of Voltaire, Diderot and d’Alembert, this movement has gained international status in the eyes of the intellectual historian.
But it remains decidedly French in its tone and manners. Clear, elegant, haughty and ironical, the ‘philosophes’, as they came to be known, stand at the end of a century in which intellectual, political and moral revolutions had upset the authority of Church and State, and humbled in their eyes all mortals whose pretensions to eminence could be backed neither by reason nor by experiment. Most of the philosophes had their intellectual roots in Cartesian scepticism; but by now this scepticism, separated from the intellectual accomplishment of the metaphysics which stemmed from it, had become a literary device, a means to sustain a detached attitude of rational unbelief, while treating of matters that could allow neither systematic development nor the easy extraction of a moral.
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.
5 - SPINOZA
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 su
bstance 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.
A Short History of Modern Philosophy: From Descartes to Wittgenstein, Second Edition Page 6