finished products, is more universal in its terms of generalization than most of the propositions of Money and Taxation can be. It seems like a paradox, that those parts of Economics in which the human elements of variable choice may predominate over the relatively fixed laws of nature and of mind, should be just the parts hardest for men to catch clearly and hold firmly; because, we naturally think, that difficulty and mystery are rather to be found in those departments in which an Infinite Mind has been at work upon an infinite plan, and that there is no such profundity in the works of men; but after all, even those natural laws like Gravitation, which are clear and universal as laws, if they be such as the devices of men have to do with, such as may be modified and in a certain sense controlled by human actions, become from that very circumstance liable to some difficulty and perhaps to some mystery. Now all the truths of Money, and as we shall see in the final chapter all the truths of Taxation also, belong to this class of less general generalizations; still, it is scarcely less than foolish to say, that Money is such an elusive and ideal agent that nobody can understand it. That is the language of indolence and lack of penetration. Money is wholly a matter of man's device, though it comes into constant contact with something greater and more fixed than itself; it was invented, just as any other instrument is invented, to accomplish a certain economical purpose; and it would be strange indeed if men by taking pains could not perfectly comprehend what men themselves have wholly devised. We hope, accordingly, in the following paragraphs to clear up completely to all intelligent readers the whole doctrine of Money. The key to unlock all the superficial difficulties (and there are no others) is this: Money is always a Valuable before it becomes money, and continues a valuable independently of the fact that it _is_ money; and, it is always one or other of two kinds, either itself a Commodity or a Promise to pay a commodity. In this chapter, we will not begin with definitions and justify them afterwards, but will come up to them step by step, and, as it were, justify them beforehand.