The Wealth of Nations by Part 2 Chapter 1 Page 13

of those machines, frequently requiring no other repairs than the most profitable application of the farmer’s capital employed in cultivating it:

Fourthly, of the acquired and useful abilities of all the inhabitants or members of the society.

The acquisition of such talents, by the maintenance of the acquirer during his education, study, or apprenticeship, always costs a real expense, which is a capital fixed and realized, as it were, in his person. Those talents, as they make a part of his fortune, so do they likewise of that of the society to which he belongs. The improved dexterity of a workman may be considered in the same light as a machine or instrument of trade which facilitates and abridges labour, and which, though it costs a certain expense, repays that expense with a profit.