In such societies, wages differ widely, but they still bear a more or less definite and obvious relation to each other. This relation is not invariable, as at one time a philosopher of repute may earn by his lectures many fold the wages of the best mechanic, and at another can hardly hope for the pay of a footman; as in a great city occupations may yield relatively high wages, which in a new settlement would yield relatively low wages; yet these variations between wages may, under all conditions, and in spite of arbitrary divergences caused by custom, law, etc., be traced to certain circumstances. In one of his most interesting chapters Adam Smith thus enumerates the principal circumstances “which make up for a small pecuniary gain in some employments and counterbalance a great one in others: First, the agreeableness or disagreeableness of the employments themselves. Secondly, the easiness and cheapness, or the difficulty and expense of learning them. Thirdly, the constancy or inconstancy of employment in them. Fourthly, the small or great trust which must be reposed in them. Fifthly, the probability or improbability of success in them.”[38] It is not necessary to dwell in detail on these causes of variation in wages between different employments. They have been admirably explained and illustrated by Adam Smith and the economists who have followed him, who have well worked out the details, even if they have failed to apprehend the main law. The effect of all the circumstances which give rise to the differences between wages in different occupations may be included as supply and demand, and it is perfectly correct to say that the wages in different occupations will vary relatively according to differences in the supply and demand of labor—meaning by demand the call which the community as a whole makes for services of the particular kind, and by supply the relative amount of labor which, under the existing conditions, can be determined to the performance of those particular services. But though this is true as to the relative differences of wages, when it is said, as is commonly said, that the general rate of wages is determined by supply and demand, the words are meaningless. For supply and demand are but relative terms. The supply of labor can only mean labor offered in exchange for labor or the produce of labor, and the demand for labor can only mean labor or the produce of labor offered in exchange for labor. Supply is thus demand, and demand supply, and, in the whole community, one must be co-extensive with the other. This is clearly apprehended by the current political economy in relation to sales, and the reasoning of Ricardo, Mill, and others, which proves that alterations in supply and demand cannot produce a general rise or fall of values, though they may cause a rise or fall in the value of a particular thing, is as applicable to labor. What conceals the absurdity of speaking generally of supply and demand in reference to