'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 [45] 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.