In relation to the mental or thinking system, “every movement,” says Cabanis, “becomes in its turn the principle or occasion of new impressions, of which the frequent repetition and the varied character must increase more and more the circle of our judgments, or tend unceasingly to rectify them. It hence follows that labour, giving to this word the most general signification, cannot but have an influence infinitely useful on the habits of the understanding, and consequently also on those of the will.” This argument is evidently applicable to varied exercise. On the contrary, “the great division of labour, so favourable to the perfecting of the arts, contracts more and more the understanding of workmen.” Exercises, moreover, inspire confidence in difficult situations, and suggest resources in danger. Their consequent influence upon the moral conduct of man is such, that, by a courage which is well founded, because it springs from a perfect knowledge of his own powers, he is often enabled to render the most important services to others. Although the direct effect of exercise is not only to confer power on the muscular and other organs, but to multiply external impressions, and to occupy with them all the senses at once; still minds thus disposed, in general occupy themselves rather with objects of imagination and sentiment, than with those which demand more complicated operation. The sense of muscular power impresses determinations which, carrying man perpetually out of himself, scarcely permit him to dwell upon impressions transmitted to his brain. The only action of that organ, during these exercises, seems to be limited to ordering the movements. Hence, exercise, especially taken in the open air, amidst new and varied objects of sight, is not favourable to reflection--to labours which demand the assemblage and concentration of all the powers of the mind. It is, on the contrary, in the absence of external impressions, that we become more capable of seizing many relations, and of following a long train of purely abstract reasoning. As life spent chiefly in active muscular exercises would leave in a state of repose those central organs that are subservient to the moral qualities and intellectual faculties, I agree with Seneca and Camper, in proscribing all such exercises, or such degrees of exercise, as would exhaust the mind, and render man incapable of aptitude in science, polite literature, and art.