If all the various faculties attributed to the soul are examined, it will be found that like those of the body they are to be ascribed to physical causes, to which it will be very easy to recur. It will be found that the powers of the soul are the same as those of the body; that they always depend on the organization of this body, on its peculiar properties, on the permanent or transitory modifications that it undergoes; in a word, on its temperament. _Temperament_ is, in each individual, the habitual state in which he finds the fluids and the solids of which his body is composed. This temperament varies, by reason of the elements or matter that predominate in him, in consequence of the different combinations, of the various modifications, which this matter, diversified in itself, undergoes in his machine. Thus, in one, the blood is superabundant; in another, the bile; in a third, phlegm, &c. It is from Nature--from his parents--from causes, which from the first moment of his existence have unceasingly modified him, that man derives his temperament. It is in his mother's womb that he has attracted the matter which, during his whole life, shall have an influence on his intellectual faculties--on his energies--on his passions--on his conduct. The very nourishment he takes, the quality of the air he respires, the climate he inhabits, the education he receives, the ideas that are presented to him, the opinions he imbibes, modify this temperament. As these circumstances can never be rigorously the same in every point for any two men, it is by no means surprising that such an amazing variety, so great a contrariety, should be found in man; or that there should exist as many different temperaments, as there are individuals in the human species. Thus, although man may bear a general resemblance, he differs essentially, as well by the texture of his fibres and the disposition of his nerves, as by the nature, the quality, the quantity of matter that gives them play, that sets his organs in motion. Man, already different from his fellow, by the elasticity of his fibres, the tension of his nerves, becomes still more distinguished by a variety of other circumstances: he is more active, more robust, when he receives nourishing aliments, when he drinks wine, when he takes exercise: whilst another, who drinks nothing but water, who takes less juicy nourishment, who languishes in idleness, shall be sluggish and feeble.