The explanation which Condillac has given appears to me to be quite unsatisfactory and empirical—in fact, it explains nothing. “From the very fact,” he says, “that an exchange is made, it follows that there must be profit for the two contracting parties, for otherwise it would not take place. Then each exchange includes two gains for humanity.” Holding this proposition as true, we see in it only the statement of a result. It is in this way that the ‹Malade Imaginaire› explains the narcotic virtue of opium:— Quia est in eo Virtus dormitiva Quæ facit dormire. Exchange includes two gains, you say. How? Why? It results from the fact that it takes place. But why does it take place? What motive has induced the contracting parties to effect the exchange? Has Exchange in itself a mysterious virtue, necessarily beneficial, and incapable of explanation? Others make the advantage consist in this, that the one gives away a commodity of which he has too much in order to receive another of which he has too little. Exchange, they say, is a ‹barter of the superfluous for the necessary›. This is contradicted by facts which pass under our own eyes; for who can say that the peasant, in giving away the corn which he has raised, but which he is never to eat, gives away a superfluity? I see in this axiom very clearly how two men may make an accidental arrangement, but I see no explanation of progress. Observation gives us a more satisfactory explanation of the power of Exchange. Exchange has two manifestations—namely, union of forces, and separation of occupations. It is very clear that in many cases the united force of several men is superior, all things considered, to the sum of their individual forces. Suppose that what is wanted is to remove a heavy load. Where a thousand men in succession may fail, it is possible that four men may succeed by uniting their efforts. Just let us reflect how few things were ever accomplished in this world without union! [p104] And yet this is only the concurrence of muscular forces in a common design. Nature has endued us with very varied physical, intellectual, and moral faculties. There are in the co-operation of these faculties endless combinations. Is it wished to accomplish a useful work, like the construction of a road, or the defence of a country? One gives the community the benefit of his strength, another of his agility, another of his courage, another of his experience, foresight, imagination, even of his reputation. It is easy to comprehend that the same men acting singly could not have attained, or even conceived, the same results. Now, union of forces implies Exchange. To induce men to co-operate, they have the prospect of participating in the benefit to be obtained. Each makes the other profit by his Efforts, and he profits by the other’s Efforts in return, which is Exchange.