Now, the economical usefulness of a thing depends not merely on its own nature, but on the number of people who can and will use it. A horse is useless, and therefore unsaleable, if no one can ride,--a sword if no one can strike, and meat, if no one can eat. Thus every material utility depends on its relative human capacity.
Similarly: The agreeableness of a thing depends not merely on its own likeableness, but on the number of people who can be got to like it. The relative agreeableness, and therefore saleableness, of "a pot of the smallest ale," and of "Adonis painted by a running brook," depends virtually on the opinion of Demos, in the shape of Christopher Sly. That is to say, the agreeableness of a thing depends on its relative human disposition.[49] Therefore, political economy, being a science of wealth, must be a science respecting human capacities and dispositions. But moral considerations have nothing to do with political economy (III. i. 2). Therefore, moral considerations have nothing to do with human capacities and dispositions.
[49] These statements sound crude in their brevity; but will be found of the utmost importance when they are developed. Thus, in the above instance, economists have never perceived that disposition to buy is a wholly _moral_ element in demand: that is to say, when you give a man half-a-crown, it depends on his disposition whether he is rich or poor with it--whether he will buy disease, ruin, and hatred, or buy health, advancement, and domestic love. And thus the agreeableness or exchange value of every offered commodity depends on production, not merely of the commodity, but of buyers of it; therefore on the education of buyers, and on all the moral elements by which their disposition to buy this, or that, is formed. I will illustrate and expand into final consequences every one of these definitions in its place: at present they can only be given with extremest brevity; for in order to put the subject at once in a connected form before the reader, I have thrown into one, the opening definitions of four chapters; namely, of that on Value ("Ad Valorem"); on Price ("Thirty Pieces"); on Production ("Demeter"); and on Economy ("The Law of the House").