The physical and moral obstacles, that Nature has interposed to the gratification of the multitudinous and constantly increasing desires of men, are so great in all directions, that the powers of the individual man are utterly unable to surmount any considerable number of them; while at the same time, the physical and moral powers, adapted under sufficient motives to overcome these obstacles, are very diverse in the different individuals of mankind. Not only is there a surprising diversity in original gifts, but also the powers acquired by gradual concentration of personal effort upon one set of obstacles become exceedingly diverse, as does moreover familiarity in the use of the gratuitous forces of nature which lend their aid towards overcoming these particular obstacles. As the result of one or two or all of these, one man naturally comes to have a vast advantage over others in his particular branch of business, whatever that may be; each of these others by precisely the same means comes to have a legitimate advantage over the first in his own branch of effort, whatever that may be; and if, as always happens practically, the first has desires which the varied efforts of the others can satisfy, and they too desires which his efforts can satisfy, nothing more is necessary to profitable exchanges between them than this diversity of relative advantage at different points. It is solely because a given effort irksome in itself put forth for another person, in view of and for the sake of a return-service from him, realizes more of satisfaction to both parties than when put forth for one's self directly, that commercial exchanges ever take place among men. The sole ground of these, the principle underlying them everywhere, is DIVERSITY OF ADVANTAGE BETWEEN DIFFERENT MEN AND BETWEEN DIFFERENT NATIONS IN DIFFERENT RESPECTS. All exchanges whatsoever depend on diversity of relative advantage in the production of commodities or services or credits as between the persons exchanging; and this diversity of relative advantage exists by God's appointment primarily among individual men as such, and only secondarily on the ground of the varied soil and climate and position and natural gifts of different parts of the earth. Reserving these secondary considerations, which are quite secondary in importance also, to a later detailed discussion, it is very clear and of central consequence in our science that a diversity of relative advantage in different things displays itself as between the individuals of every community and country large and small. There is no hamlet in any land in which one man has not an advantage over his neighbors in the making of clothes, another in the making and setting of horse-shoes, a third in the building of houses, a fourth in the curing of diseases, and another in the keeping a school; while each of those neighbors has undoubtedly some advantage or other over each of these in some trade or means of livelihood.