Political economists generally, and English political economists above others, have been accustomed to lay almost exclusive stress upon the first of [two] agencies [competition and custom]; to exaggerate the effect of competition, and to take into little account the other and conflicting principle. They are apt to express themselves as if they thought that competition actually does, in all cases, whatever it can be shown to be the tendency of competition to do. This is partly intelligible, if we consider that only through the principle of competition has political economy any pretension to the character of a science. So far as rents, profits, wages, prices, are determined by competition, laws may be assigned for them. Assume competition to be their exclusive regulator, and principles of broad generality and scientific precision may be laid down, according to which they will be regulated. The political economist justly deems this his proper business: and, as an abstract or hypothetical science, political economy can not be required to do, and indeed can not do, anything more. But it would be a great misconception of the actual course of human affairs to suppose that competition exercises in fact this unlimited sway. I am not speaking of monopolies, either natural or artificial, or of any interferences of authority with the liberty of production or exchange. Such disturbing causes have always been allowed for by political economists. I speak of cases in which there is nothing to restrain competition; no hindrance to it either in the nature of the case or in artificial obstacles; yet in which the result is not determined by competition, but by custom or usage; competition either not taking place at all, or producing its effect in quite a different manner from that which is ordinarily assumed to be natural to it. As stated by Mr. Cairnes,(161) political economy is a science just as is any recognized physical science—astronomy, chemistry, physiology. The economic “facts we find existing are the results of causes, between which and them the connection is constant and invariable. It is, then, the constant relations exhibited in economic phenomena that we have in view when we speak of the laws of the phenomena of wealth; and in the exposition of these laws consists the science of political economy.” It is to be remembered that economic laws are _tendencies_, not actual descriptions of any given conditions in this or that place.