I, at least, can fully accept their general view. I quite agree that the old assumptions of the older school were frequently unjustifiable; nor can I deny that they laid them down with a tone of superlative dogmatism, which was apt to be very offensive, and which was not justified by their position. Moreover, I entirely agree that the progress of economic science, and of all other moral sciences, requires a historical basis; and that we should make a very great blunder if we thought that the creation of an economic man would justify us in dispensing with an investigation of concrete facts, both of the present day and of earlier stages of industrial evolution. But to this there is an obvious qualification. What do we mean by investigating facts? It seems to be a very simple rule, but it leads us at once to great difficulties. So, as Mill and later writers have very rightly asked, how are we to settle even the most obvious questions in inquiries where, for obvious reasons, we cannot make experiments, and where we have not such a set of facts as would spontaneously give us the truths which we might seek by experiment? Take, as Mill suggested, such a question as free trade. We cannot get two countries alike in all else, and differing only in respect to their adoption or rejection of a protective tariff. Anything like a thoroughgoing system of free trade has been tried in England alone; and the commercial prosperity of the country since its adoption has been affected by innumerable conditions, so that it is altogether impossible to isolate the results which are to be attributed to the negative condition of the absence of protection. Briefly, the result is that the phenomena with which we have to deal are so complex, and our power of arranging them so as to unravel the complexity is so limited, that the direct method of observation breaks down altogether. Mill confessed the necessity of applying a different method, which he described with great ability, and which substantially amounts to the method of the older Economists. If, with some writers of the historical school, we admit the objections which apply to this method, we seem to be reduced to a hopeless state of uncertainty. A treatise on Political Economy becomes nothing but a miscellaneous collection of facts, with no definite clue or uniform method of reasoning. I must beg, in conclusion, to indicate what, so far as I can guess, seems to be the view suggested in presence of this difficulty.