Smith’s first theory makes the true value of any commodity depend upon the amount of labour or effort it has taken to produce. “Labour, therefore, is the real measure of the exchangeable value of all commodities.” “The real price of every thing, what every thing really costs to the man who wants to acquire it, is the toil and trouble of acquiring it.”[178] Labour—that is, the effort expended upon the production of a commodity—is both the origin and the measure of its exchange value. The theory that labour or effort is the cause of value (if value can be said to have a cause) was first formulated by the father of political economy himself. It is curious to think that it was this same theory that was used with such good effect by Karl Marx in his attack upon capitalism. This first attempt to find a firmer foundation for exchange value than that afforded by the shifting sands of demand and supply was scarcely made before Smith became aware of some difficulties in the path. For example, how was this work and the value dependent upon it to be measured? “There may be more labour in an hour’s hard work than in two hours’ easy business; or in an hour’s application to a trade which it cost ten years’ labour to learn, than in a month’s industry at an ordinary and obvious employment. But it is not easy to find any accurate measure either of hardship or ingenuity.”[179] A second objection arises when the theory is applied to civilized society. Work by itself cannot produce anything; something must be contributed by both land and capital. But neither of these is a free good, and they must cost something to those who employ them. Accordingly primitive societies[180] are the only ones where “the quantity of labour commonly employed in acquiring or producing any commodity is the only circumstance determining its value.” We must nowadays take some account of land and capital. So that labour is not the only source of value, nor is it its sole measure.