All these causes have necessarily an influence on the mind, on the passions, on the will; in a word, on what are called the intellectual faculties. Thus, it may be observed, that a man of a sanguine constitution, is commonly lively, ingenious, full of imagination, passionate, voluptuous, enterprising; whilst the phlegmatic man is dull, of a heavy understanding, slow of conception, inactive, difficult to be moved, pusillanimous, without imagination, or possessing it in a less lively degree, incapable of taking any strong measures, or of willing resolutely. If experience was consulted, in the room of prejudice, the physician would collect from morals, the key to the human heart: in curing the body, he would sometimes be assured of curing the mind. Man, in making a spiritual substance of his soul, has contented himself with administering to it spiritual remedies, which either have no influence over his temperament, or do it an injury. The doctrine of the spirituality of the soul has rendered morals a conjectural science, that does not furnish a knowledge of the true motives which ought to be put in activity, in order to influence man to his welfare. If, calling experience to his assistance, man sought out the elements which form the basis of his temperament, or of the greater number of the individuals composing a nation, he would then discover what would be most proper for him,--that which could be most convenient to his mode of existence--which could most conduce to his true interest--what laws would be necessary to his happiness--what institutions would be most useful for him--what regulations would be most beneficial. In short, morals and politics would be equally enabled to draw from _materialism_, advantages which the dogma of spirituality can never supply, of which it even precludes the idea. Man will ever remain a mystery, to those who shall obstinately persist in viewing him with eyes prepossessed by metaphysics; he will always be an enigma to those who shall pertinaciously attribute his actions to a principle, of which it is impossible to form to themselves any distinct idea. When man shall be seriously inclined to understand himself, let him sedulously endeavour to discover the matter that enters into his combination, which constitutes his temperament; these discoveries will furnish him with the clue to the nature of his desires, to the quality of his passions, to the bent of his inclinations--will enable him to foresee his conduct on given occasions--will indicate the remedies that may be successfully employed to correct the defects of a vicious organization, of a temperament, as injurious to himself as to the society of which he is a member.