'Fancy to yourself an animal created by God and designed to sing continually. It will always sing, that is most certain; but if God designs him a certain tablature, he must necessarily either put it before his eyes or imprint it upon his memory or dispose his muscles in such a manner that according to the laws of mechanism one certain note will always come after another, agreeably to the order of the tablature. Without this one cannot apprehend
that the animal can always follow the whole set of the notes appointed him by God. Let us apply this to man's soul. M. Leibniz will have it that it has received not only the power of producing thoughts continually, but also the faculty of following always a certain set of thoughts, which answers the continual changes that happen in the machine of the body. This set of thoughts is like the tablature prescribed to the singing animal above mentioned. Can the soul change its perceptions or modifications at every moment according to such a set of thoughts, without knowing the series of the notes, and actually thinking upon them? But experience teaches us that it knows nothing of it. Were it not at least necessary that in default of such a knowledge, there should be in the soul a set of particular instruments, each of which would be a necessary cause of such and such a thought? Must they not be so placed and disposed as to operate precisely one after another, according to the correspondence pre-established between the changes of the body and the thoughts of the soul? but it is most certain that an immaterial simple and indivisible substance cannot be made up of such an innumerable multitude of particular instruments placed one before another, according to the order of the tablature in question. It is not therefore possible that a human soul should execute that law.
'M. Leibniz supposes that the soul does not distinctly know its future perceptions, but that it perceives them confusedly, and that there are in each substance traces of whatever hath happened, or shall happen to it: but that an infinite multitude of perceptions hinders us from distinguishing them. The present state of each substance is a natural consequence of its preceding state. The soul, though never so simple, has always a sentiment composed of several perceptions at one time: which answers our end as well as though it were composed of pieces, like a machine. For each foregoing perception has an influence on those that follow agreeably to a law of order, which is in perceptions as well as in motions...The perceptions that are together in one and the same soul at the same time, including an infinite multitude of little and indistinguishable sentiments that are to be unfolded, we need not wonder at the infinite variety of what is to result from it in time. This is only a consequence of the representative nature of the soul, which is, to express what happens and what will happen in its body, by the connexion and correspondence of all the parts of the world. I have but little to say in answer to this: I shall only observe that this supposition when sufficiently cleared is the right way of solving all
the difficulties. M. Leibniz, through the penetration of his great genius, has very well conceived the extent and strength of this objection, and what remedy ought to be applied to the main inconveniency. I do not doubt but that he will smooth the rough parts of his system, and teach us some excellent things about the nature of spirits. Nobody can travel more usefully or more safely than he in the intellectual world. I hope that his curious explanations will remove all the impossibilities which I have hitherto found in his system, and that he will solidly remove my difficulties, as well as those of Father Lami. And these hopes made me say before, without designing to pass a compliment upon that learned man, that his system ought to be looked upon as an important conquest.
'He will not be much embarrassed by this, viz. that whereas according to the supposition of the Cartesians there is but one general law for the union of spirits and bodies, he will have it that God gives a particular law to each spirit; from whence it seems to result that the primitive constitution of each spirit is specifically different from all others. Do not the Thomists say, that there are as many species as individuals in angelic nature?'
Leibniz acknowledged Bayle's note in a further reply, which is written as though for publication. It was communicated to Bayle, but it was not in fact published. It is dated 1702. It may be found in the standard collections of Leibniz's philosophical works. It reads almost like a sketch for the Theodicy.
The principal point developed by Leibniz is the richness of content which, according to him, is to be found in each 'simple substance'. Its simplicity is more like the infinitely rich simplicity of the divine Being, than like the simplicity of the atom of Epicurus, with which Bayle had chosen to compare it. It contains a condensation in confused idea of the whole universe: and its essence is from the first defined by the part it is to play in the total harmony.
As to the musical score ('tablature of notes') which the individual soul plays from, in order to perform its ordained part in the universal harmony, this 'score' is to be found in the confused or implicit ideas at any moment present, from which an omniscient observer could always deduce what is to happen next. To the objection 'But the created soul is not an omniscient observer,
and if it cannot read the score, the score is useless to it', Leibniz replies by affirming that much spontaneous action arises from subjective and yet unperceived reasons, as we are all perfectly aware, once we attend to the relevant facts. All he claims to be doing is to generalize this observation. All events whatsoever arise from the 'interpretation of the score' by monads, but very little of this 'interpretation' is in the least conscious.
Leibniz passes from the remarks about his own doctrine under the article 'Rorarius' to other articles of Bayle's dictionary, and touches the question of the origin of evil, and other matters which receive their fuller treatment in the Theodicy.