Whence can arise the uniformity that is in all the works of animals? Why does each species invariably perform the same actions in the same manner? And why does not one individual perform them better or worse than another? Can there be a stronger proof that their operations are merely the effects of mechanism and materiality? If they possessed the smallest spark of that light which is inherent in mankind, their works would display variety at least, if not perfection, and one individual would, in its performance, make some little difference from what another had done. But this is far from being the case. One plan of action is common to the whole species, and whoever would attribute a mind or soul to animals, must of necessity allow but one to each species, of which each individual would be an equal partaker, and as thereby it would be divisible, it would consequently be material, and of a nature widely different from ours. Why, on the other hand, are the productions and performances of men so various, and so diversified? Why is a servile imitation more troublesome to us than an original design? It is because our souls are our own, and independent of any other, and because we have nothing in common with our species but the matter which forms our body, and in which our resemblance to brute animals is confined. Were internal sensations dependent on corporeal organs, should we not see as remarkable difference in the works of animals of the same species as in those of men? Would not those which were the most happily organized, build their nests and contrive their cells in a manner more solid, elegant, and commodious? And if any individual possessed a superior genius, would it not take an opportunity to manifest that superiority in its actions? But nothing of this kind has ever happened, and therefore the corporeal organs, however perfect or imperfect, have no influence on the nature of the internal sensations. Hence we may conclude, that animals have no sensations of this kind; that such sensations have no connection with matter, no dependence in their nature on the texture of corporeal organs, and that of consequence there must be a substance in man different from matter, which is the subject and the cause that produces and receives those sensations.