Adam Smith's chapters on division of labour are so well known that there is no need to point out the very great economic benefits that arise from it. Clearly, any man who spends all his working time upon one particular process of productive activity acquires thereby a skill and rapidity in carrying out his part of the operation which would be impossible to any worker who has to carry the manufacture of an article from the beginning to its end. Just as we saw, when the primitive savage left off doing everything for himself and took to building huts for the rest of the community, that the huts became much more water-tight and comfortable, so the process goes still further, and building becomes very much more rapid and very much more cheap and efficient when a large number of specialists are set to work on the various very different processes required for the construction of a house. The consequence is that the production of goods is very greatly cheapened and made much more rapid, but at the same time the worker tends to become an artisan instead of a craftsman, and his work is likely to be much more monotonous and much more trying. Instead of seeing his product grow under his hand from its beginning to its end, with constant changes in the nature of its call on his energy and care, he is employed during the whole of his working time on some mechanical process, with the result that he himself becomes something very like a machine. What he has gained in the power to make and acquire commodities cheaply and quickly is offset to a certain extent by the less interesting and varied nature of his work. It also follows that as the worker becomes a specialist he becomes dependent upon other members of the community for the supply to him of a large number of things which he requires for his own existence. If he spends his life in making one commodity or in making part of one commodity, it is clear that his requirements of all the things that are necessary for life apart from what he makes himself can only be satisfied by the willingness of the community to take the commodity that he makes in payment for those which it produces and of which he is in need. When he works for himself, he only makes things that he knows himself to need; when he works to sell to others, he has to speculate on the hope that the others will want what he makes. Commerce thus not only shows the unity of mankind by being a universal feature of his existence, but increases that unity by making each individual dependent upon the exertions of his fellows, and on their willingness to take from him stuff which he is turning out; but if commerce thus promotes unity, it also tends to create a certain amount of friction and disagreement between one man and another when differences of opinion arise concerning the value of the product which each man is making, that is to say, concerning the amount of goods which the rest of the community is prepared to give him in exchange.