Conclusiones Parciales

The doctrine of pre-established harmony may seem nowadays to be no more than a baroque piece of metaphysical speculation; but it should be clear from what has already been said that, far from being something 'tacked on' to the rest of his system, the doctrine flows from certain central assumptions which Leibniz makes about the nature of predication and the uniqueness of each substance. Moreover, the moves which Leibniz makes in arriving at the doctrine are but one set of variations on an enduring theme of seventeenth and eighteenth-century philosophy: the problem

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of how to analyse the notion of causality. The rationalism of Descartes and Spinoza required, as we have seen, that there be some intelligible 'connection' between cause and effect--a connection which would make it possible, in principle, to demonstrate that a certain effect must of necessity follow from a certain cause. Nicolas Malebranche gave precise expression to this view in his Recherche de la vérité, when he wrote that 'a true cause is one such that the mind perceives a necessary connection between it and its effect'. ⁶³

On its strongest interpretation, this thesis (which we may call the 'Connection Thesis') leads to the conclusion that only God can count as a true cause, since only the effects produced by an omnipotent being are strictly and absolutely necessary (it being a contradiction to suppose that what God decides to bring about does not occur). This is exactly the line taken by Malebranche. Modern readers may be sceptical about such 'absolute' necessity, but may be inclined to allow that effects are necessitated in the weaker 'hypothetical' sense that they are deducible from explanatory laws or principles (as the conclusions of a valid argument are deducible from the premisses). But this weak notion of deducibility could be satisfied by an argument of the form 'Whenever C then E; C; therefore E', where the first premiss has the status of a mere contingent generalization. The rationalists wanted something stronger:

ideally, they wanted the effects to be directly deducible from the causes alone (see above, pp.

55-9). The explanatory premisses or principles invoked were themselves required to be as transparent to the intellect as the principles of mathematics. This seems to be part of the rationale behind the 'causal similarity' requirement--that a cause must be of the same kind as its effect: we can, it is supposed, 'see' how like gives rise to like (how motion produces further motion, or a thought generates further thoughts), but we cannot understand how two utterly heterogeneous substances could be causally related.

Against this background, it is easy enough to see, given that Leibnizian substances are all different in kind (each being its own 'infima species'), that there is no room for any causal interaction of a kind which would satisfy the rationalist insistence on a transparent connection between cause and effect. Hence for

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Leibniz, there simply cannot be causal transactions, but only a pre-programmed harmony. The only alternatives, as Leibniz saw it, were either to posit some kind of mysterious 'influx'--an occult transaction between cause and effect, which was repugnant to his rationalist principles--or else to adopt the Malebranchian solution of giving God all the work to do. The former notion, that of an inflow or influx between cause and effect (an influxus physicus), had been proposed by the scholastic philosopher Francisco Suarez in his Metaphysical Disputations ( 1597); Leibniz dismissed it as a 'barbarous notion. . . . metaphorical and more obscure than what it defines' ( GP IV. 150; L126). ⁶⁴ The second, Malebranchian alternative Leibniz rejected as an ad hoc expedient, the invoking of a 'deus ex machina' ( CO521; P90).

But although Leibniz's solution does not have God perpetually springing on to the stage (every time, for example, that a body is caused to move), it does none the less give God a central (if rather less busy) role to play. For without appeal to the divine purpose of producing maximum harmony, there would be no explanation for the remarkable 'concomitance' (to use a term Leibniz at one point employs: CO521; P91) between event A (what we normally call a cause) and event B (what we normally call an effect). It is perhaps natural to wonder at this point whether it might not be better to abandon the Connection Thesis altogether. Why not propose, as David Hume was to suggest not long afterwards, that despite our strong

psychological propensity to believe in some necessary link between cause and effect, all that actually occurs in nature is a mere regular concomitance or conjunction of events .⁶⁵ Leibniz's answer is contained in a remarkable passage in the Monadology, which in many ways

anticipates the Humean line on causation:

When dogs are shown a stick they remember the pain it has caused them in the past and howl or run away . . . Often a vivid impression has in a moment the effect of long habit, or of many perceptions long repeated. Men act like brutes in so far as the sequences of their perceptions arise through the principle of memory only, like those empirical physicians who have mere practice without theory. We are all merely empiricists as regards three-fourths of our actions.

For example, when we expect it to be day tomorrow, we are behaving as empiricists, because until now it

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has always happened thus. The astronomer, however, knows by reason ... It is the knowledge of and eternal truths which distinguishes us from the animals, and gives us reason and the sciences (paras. 26-9).

There could be no clearer statement of Leibniz's faith in the rational foundation of science and his rejection of what was to become the Humean line, that it is habit not reason that is the basis of our expectations and predictions about the world. This is no place for an

'adjudication' between these two philosophical positions--especially since the sense in which science can be said to be rational is a matter on which philosophers today have reached no clear consensus. ⁶⁶ What is clear, as far as Leibniz is concerned, is that his commitment to the

rational intelligibility of the universe is firmly grounded in his belief in the existence of the chief monad, or 'supreme substance', God. It is the creative selection God makes in

accordance with the 'principle of fitness or the choice of the best' (para. 46) that guarantees the ordered harmony of things.

Although God has a central place in the Leibnizian system, there are some aspects of

Leibniz's theory of substance which initially tend to suggest an independent and self-sufficient universe. Since monads are active substances (containing their principle of action within themselves), they do not, like Cartesian matter, require a God in order to have their initial motions imparted to them (contrast Descartes, Principles II, 36). Furthermore, they are like the ultimate units of the ancient Greek atomists in being indivisible and having no parts, and Leibniz takes it (following a traditional line of argument) that this implies that they are incorruptible: they 'cannot begin or end naturally' and consequently they last as long as the universe ( GP VI. 598; P195). Handled differently, these ingredients might have formed the material for a materialistic and atheistic philosophy of the kind developed by the Greek

atomist Democritus and popularized by Lucretius. ⁶⁷ But in the Leibnizian universe, things are radically different, for two main reasons.

First, unlike the inanimate and sterile particles of the atomists, Leibniz's monads are described as being alive: 'There is nothing sterile, nothing dead in the universe'; 'in the least part of matter

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there is a world of . . . living things, animals, entelechies and souls' ( Monadology, paras. 69 and 66). The implications of this 'panpsychism', as it is often (somewhat misleadingly) called, will be examined when we come to discuss Leibniz's views on mind and matter in the next chapter. Suffice it to say here that despite Leibniz's frequent insistence that monads are to be compared to 'souls', he is certainly not committed to the extreme view that every substance has consciousness. Most monads are described as having 'perceptions' only in the attenuated sense that their structure mirrors that of the entire universe; only as we go up the hierarchy to those 'dominant monads' that are entitled to be called 'minds' do we reach true consciousness ( GP VI. 599-601; P196-8).

The second reason why Leibniz regarded his substances as fundamentally different from the eternal and self-sufficient particles on which the materialists based their universe concerns the question of existence. Although monads contain within themselves everything that is true of them, there is one exception: they do not contain the reason for their own existence. They are contingent beings, and, as Leibniz says in an early paper, 'a reason must be given why

contingent beings should exist rather than not exist'. He goes on: 'but there would be no such reason unless there were a being which is in itself, that is, a being the reason for whose existence is contained in its own essence' ( GP VII. 310; P77). This reasoning, Leibniz explained in a paper entitled 'Of the Ultimate Origin of Things' ( 1697), is not affected by the supposition that the universe is eternal:

Even if you suppose the world eternal, you will still be supposing nothing but a succession of states, and will not in any of them find a sufficient reason; so it is evident that the reason must be sought elsewhere . . . From this it is evident that . . . we cannot escape the ultimate

extramundane reason of things, or God ( GP VII. 302; P137).

This argument (the 'argument from contingency', as it is called) was not invented by Leibniz,

68 though it is perhaps fair to say that by linking it to one of the fundamental principles of his philosophy, the principle of sufficient reason, he made it distinctively his own. What is striking, however, as we come to the end

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of this review of the notion of substance in Descartes, Spinoza, and Leibniz, is that all three philosophers, though taking different routes, end up by placing at the heart of their systems the notion of a necessary being, a being who contains within himself the reason for his existence (though Spinoza of course rejected the notion that this being must be something outside the world or 'extra-mundane'). The affirmation of an ultimate substance in the primary sense of 'a thing that exists in such a way as to depend on nothing else for its existence' ( Descartes, Principles I, 51) forms common ground for all three philosophers. It is perhaps this fact above all others which marks a gulf between the thinking of the great seventeenth-century rationalists and our own world view, notwithstanding all the 'modern' aspects of their thought, and the role they played in the philosophical and scientific revolution which laid the

foundations for much of our modern outlook on the world. For it seems inconceivable that a philosophical system founded on the notion of a necessarily existing substance could find acceptance today (and indeed the very idea of a complete philosophical system embracing all aspects of explanation-metaphysical, ethical, and scientific--has itself ceased to be a viable possibility nowadays). However that may be, the metaphysical core which is common to the thinking of Descartes, Spinoza, and Leibniz did not prevent their taking widely divergent positions regarding the nature and explanation both of the physical world and of its relation to the phenomena of human consciousness. It is to these areas that we must now turn.

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