There is a remarkable ancient work extant, which is, as far as I am aware, the earliest regular treatise on an economical question.

It is termed the "Eryxias," or "On Wealth." The purport of this dialogue is this. The Syracusans had sent an embassy to Atheus, and the Athenians had sent a return embassy to Syracuse. As the ambassadors were entering the city, on their return from Syracuse, they met Socrates and a party of his friends, with whom they entered into conversation. Eryxias, one of the envoys, said that he had seen the richest man in all Sicily. Socrates immediately started a discussion on the nature of wealth. Eryxias said that he thought upon the subject as every one else did, and that to be wealthy meant to have much money. Socrates asked him what kind of money he meant, and he described the money of various countries. At Carthage they used as money leather discs, in which something was sewn up, but no one knew what it was, and he who possessed the greatest quantity of this money at Carthage was the richest man there; but at Athens he would be no richer than if he had so many pebbles from the hill. At Lacedæmon they used iron as money, and that useless iron. He who possessed a great quantity of this at Sparta would be wealthy, but anywhere else it would be worth nothing. In Æthiopia again, they used carved pebbles, which were of no use anywhere else.

Thus Socrates showed that money is wealth only in those places where it is exchangeable, or has purchasing power. In those places where it is not exchangeable, or has not purchasing power, it is not wealth.

Socrates then asked, "Why are some things wealth, and some things are not wealth?" "Why are some things wealth in some places and not in others, and at some times and not others?" He then showed that whether things are wealth or not depends entirely upon human wants and desires; that everything is wealth where it is wanted and demanded; and that it is not wealth where it is not wanted and demanded.

Socrates then showed that things are or wealth, only when and where they are that is, where they are wanted and demanded.

Thus, though some persons might be puzzled at the meaning of the word wealth, there is no possibility of mistake when we refer to the Greek, because which is one of the most usual words for wealth in Greek, comes from to want or demand; consequently the word or wealth, means simply anything whatever which is wanted and demanded, no matter what its nature or its form may be.

It is, then, human wants and desires which alone constitute anything as wealth: anything whatever which men want and demand, and are willing to pay for, is wealth, whatever its nature may be : anything which no one wants and demands is not wealth.

Socrates then showed that anything else which enables us to purchase what we want and demand is wealth, for exactly the same reason that gold and silver are.

He instanced professors and persons who gained their living by giving instruction in the various sciences. He said that persons got what they wanted in exchange for this instruction, just as they did for gold and silver; and consequently, he said, the sciences are wealth - and that those who are masters of such sciences are so much the richer -

Now, in instancing the sciences as wealth, that of course is a general term for labour, because labour, in economics, is any exertion of human ability, or thought, which is wanted, demanded, and paid for. Now, labour or thought cannot be seen or handled, but it can be bought and sold: its value can be measured in money, and therefore, by Aristotle's definition, it is wealth.

Socrates, in this dialogue, shows that the mind has wants and demands as well as the body, and that the services which are wanted and demanded by the mind, and are paid for, are equally wealth, as those material commodities which satisfy the wants and demands of the body and are paid for.

Thus Socrates shows that personal qualities are wealth, and a person makes an income by the exertion of his skill and labour as an advocate, a physician, an engineer, or the manager of a great company, just in the same way as another person makes an income by selling material commodities.