Concerning it, we must ask three questions: 1. Is this separation practicable, and in consequence are the results true or approximately true? 2. Under what limitations is it useful to make such a separation, and what real guidance to conduct, if any, follows? 3. Afterwards we will inquire to what extent the political economists have rigidly confined themselves to theory, and having found that they did not, when they went over into practical advice we will ask whether they were deluded by the results they had reached within their limits, and whether they hastily assumed that they had found a more complete guide to human action than they had. Is then the separation of dealings which can be expressed in terms of money from the other dealings of life sufficiently possible to make a science of those dealings? Are they predictable, given the circumstances? Will like causes produce like results? Is the motive measured by money sufficiently separable from other motives, to be treated by itself? We must at once admit that such separation cannot be absolute; that affection, pity, charity, habit, ignorance, legislative restriction, public spirit, prevent the individual from always acting according to his economic interests. He does not always buy in the cheapest shop; he grumbles but helps a struggling neighbour by his custom, and puts up for some time with an inferior article. He goes on using old machinery for want of knowledge or of a progressive mind. He keeps on an old hand for the sake of the past. Still, in the long run, these qualifications to the general law do not survive. In general, men in the large may be trusted to do that which it is their economic interest to do, within such lines of honesty as are ratified by law, or of honour as are regarded by public opinion. Competition, that is, is the general rule in business; and we shall not go far wrong in assuming it as the method in vogue in Europe and America, unless some special feature of monopoly or legislative Protection or trade combination supersedes it. This is not the same as saying that it is always right to follow the lines of pure competition. We must at all points check the tendency to pass from the indicative to the imperative mood, from a science to an art; from what will raise our profits to what is our duty in our business. So we assert that there is a Theory of Value, and that it is an approximately verified theory under the present system of business. Further, that in 1860, when business was less regulated than it is now, the results were so much nearer verification by experience. That business is carried on for self-interest on the whole, seems to me a safe approximation to reality--and that the exceptions to it are not chemically explosive of its system as Ruskin says, but can be added to the enquiry afterwards, like friction or the resistance of the air in mechanics.