On his long journey through life, from the cradle to the grave, man has need to assimilate to himself a prodigious quantity of alimentary substances, to protect himself against the inclemency of the weather, to preserve himself from a number of ailments, or cure himself of them. Hunger, thirst, disease, heat, cold, are so many obstacles strewn along his path. In a state of isolation he must overcome them all, by hunting, fishing, tillage, spinning, weaving, building; and it is clear that it would be better for him that these obstacles were less numerous and formidable, or, better still, that they did not exist at all. In society, he does not combat these obstacles personally, but others do it for him; and in return he employs himself in removing one of those obstacles which are encountered by his fellow-men. It is clear also, considering things in the gross, that it would be better for men in the aggregate, or for society, that these obstacles should be as few and feeble as possible. But when we come to scrutinize the social phenomena in detail, and men's sentiments as modified by the introduction of exchange, we soon perceive how they have come to confound wants with wealth, the obstacle with the cause. The separation of employments, the division of labour, which results from the faculty of exchanging, causes each man, instead of struggling on his own account to overcome all the obstacles which surround him, to combat only _one_ of them; he overcomes that one not for himself but for his fellow-men, who in turn render him the same service. The consequence is that this man, in combating this obstacle which it is his special business to overcome for the sake of others, sees in it the immediate source of his own wealth. The greater, the more formidable, the more keenly felt this obstacle is, the greater will be the remuneration which his fellow-men will be disposed to accord him; that is to say, the more ready will they be to remove the obstacles which stand in his way.