Pierre Bayle was the son of a Calvinist pastor, early converted to Catholicism, but recovered to his old faith after a short time. He held academic employments in Switzerland and Holland; he promoted and edited the Nouvelles de la République des Lettres, and he produced that extraordinary work the Historical and Critical Dictionary. The notices it contains of authors and thinkers are little more than pegs upon which Bayle could hang his philosophical reflexions. He could write an intelligent discussion on any opinion; what he could not do was to reconcile the points of view from which he felt impelled to write upon this author and that. His was not a systematic mind. So far as he had a philosophical opinion, he was a Cartesian; in theology he was an orthodox Calvinist. He could not reconcile his theology with his Cartesianism and he did not try to. He made a merit of the oppositions of faith to reason and reason to itself, so that he could throw himself upon a meritorious and voluntary faith.
There is nothing original in this position. It was characteristic of decadent scholasticism, it squared with Luther's exaggerations about the impotence of reason in fallen man, and Pascal had given his own highly personal twist to it. Bayle has been hailed as a forerunner of Voltairean scepticism. It would be truer to say that a Voltairean sceptic could read Bayle's discussions in his own sense and for his own purposes if he wished. But Bayle was not a sceptic. It is hard to say what he was; his whole position as between faith and reason is hopelessly confused. He was a scholar, a wit, and a philosophical sparring-partner of so perfectly convenient a kind that if we had not evidence of his historical reality, we might have suspected Leibniz of inventing him.
In the first edition of his Dictionary, under the article 'Rorarius', Bayle gave a very fair account of Leibniz's doctrine concerning the souls of animals, as it could be collected from his article in the Journal des Savants, 27 June 1695. He then proceeded to comment upon it in the following terms:
'There are some things in Mr. Leibniz's hypothesis that are liable to some difficulties, though they show the great extent of his genius. He will have it, for example, that the soul of a dog acts independently of outward bodies; that it stands upon its own bottom, by a perfect spontaneity with respect to itself, and yet with a perfect conformity to outward things. … That its internal perceptions arise from its original constitution, that is to say, the representative constitution (capable of expressing beings outside itself in relation to its organs) which was bestowed upon it from the time of its creation, and makes its individual character (Journal des Savants, 4 July 1695). From whence it results that it would feel hunger and thirst at such and such an hour, though there were not any one body in the universe, and though nothing should exist but God and that soul. He has explained (Histoire des Ouvrages des Savants, Feb. 1696) his thought by the example of two pendulums that should perfectly agree: that is, he supposes that according to the particular laws which put the soul upon action, it must feel hunger at such an hour; and that according to the particular laws which direct the motion of matter, the body which is united to that soul must be modified at that same hour as it is modified when the soul is hungry. I will forbear preferring this system to that of occasional causes till the learned author has perfected it. I cannot apprehend the connexion of internal and spontaneous actions which would have this effect, that the soul of a dog would feel pain immediately after having felt joy, though it were alone in the universe. I understand why a dog passes immediately from pleasure to pain when, being very hungry and eating a piece of bread, he is suddenly struck with a cudgel. But I cannot apprehend that his soul should be so framed that at the very moment of his being beaten he should feel pain though he were not beaten, and though he should continue to eat bread without any trouble or hindrance. Nor do I see how the spontaneity of that soul should be consistent with the sense of pain, and in general with any unpleasing perceptions.
'Besides, the reason why this learned man does not like the Cartesian system seems to me to be a false supposition; for it cannot be said that the system of occasional causes brings in God acting by a miracle (ibid.), Deum ex machina, in the mutual dependency of the body and soul: for since God does only intervene according to general laws, he cannot be said to act in an extraordinary manner. Does the internal and active virtue communicated to the forms of bodies according to M. Leibniz know the train of actions which it is to produce? By no means; for we know by experience that we are ignorant whether we shall have such and such perceptions in an hour's time. It were therefore necessary that the forms should be directed by some internal principle in the production of their acts. But this would be Deus ex machina, as much as in the system of occasional causes. In fine, as he supposes with great reason that all souls are simple and indivisible, it cannot be apprehended how they can be compared with a pendulum, that is, how by their original constitution they can diversify their operations by using the spontaneous activity bestowed upon them by their Creator. It may clearly be conceived that a simple being will always act in a uniform manner, if no external cause hinders it. If it were composed of several pieces, as a machine, it would act different ways, because the peculiar activity of each piece might change every moment the progress of others; but how will you find in a simple substance the cause of a change of operation?'
Leibniz published a reply to Bayle in the Histoire des Ouvrages des Savants for July 1698. As in all his references to Bayle, he is studiously polite and repays compliment for compliment. The following are perhaps the principal points of his answer.
1. On the example of the dog:
(a) How should it of itself change its sentiment, since everything left to itself continues in the state in which it is? Because the state may be a state of change, as in a moving body which, unless hindered, continues to move. And such is the nature of simple substances—they continue to evolve steadily.
(b) Would it really feel as though beaten if it were not beaten, since Leibniz says that the action of every substance takes place as though nothing existed but God and itself? Leibniz replies that his remark refers to the causality behind an action, not to the reasons for it. The spontaneous action of the dog, which leads to the feeling of pain, is only decreed to be what it is, for the reason that the dog is part of a world of mutually reflecting substances, a world which also includes the cudgel.
(c) Why should the dog ever be displeased spontaneously? Leibniz distinguishes the spontaneous from the voluntary: many things occur in the mind, of itself, but not chosen by it.
2. On Cartesianism and miracle:
Cartesianism in the form of occasionalism does involve miracle, for though God is said by it to act according to laws in conforming body and mind to one another, he thereby causes them to act beyond their natural capacities.
3. On the problem, how can the simple act otherwise than uniformly?
Leibniz distinguishes: some uniform action is monotonous, but some is not. A point moves uniformly in describing a parabola, for it constantly fulfils the formula of the curve. But it does not move monotonously, for the curve constantly varies. Such is the uniformity of the action of simple substances.
Bayle read this reply, and was pleased but not satisfied with it. In the second edition of the dictionary, under the same article 'Rorarius', he added the following note:
'I declare first of all that I am very glad I have proposed some small difficulties against the system of that great philosopher, since they have occasioned some answers whereby that subject has been made clearer to me, and which have given me a more distinct notion of what is most to be admired in it. I look now upon that new