Ý tưởng kết thúc, mà là nền tảng cho quan niệm của chúng ta về kinh tế, không thể định nghĩa về hành vi bên ngoài mà thôi. Nếu chúng ta để giải thích mối quan hệ phát sinh từ sự tồn tại của một tình trạng khan hiếm các phương tiện liên quan đến đa dạng của kết thúc, | 88 SIGNIFICANCE OF ECONOMIC SCIENCE OH. like in terms of inner experience. The idea of an end which is fundamental to our conception of the economic is not possible to define in terms of external behaviour only. If we are to explain the relationships which arise from the existence of a scarcity of means in relation to a multiplicity of ends surely at least one-half of the equation as it were must be psychical in character. Such considerations would be decisive so long as it were taken for granted that the definition of the subjectmatter of Economics suggested in this essay was correct. But it might be urged that they were simply an argument for rejecting that definition and substituting one relating only to objective observable matters market prices ratios of exchange and so on. This is clearly what is implied by Professor Cassel s procedure the celebrated Ausschaltung đer Wertlehre. But even if we restrict the object of Economics to the explanation of such observable things as prices we shall find that in fact it is impossible to explain them unless we invoke elements of a subjective or psychological nature. It is surely clear as soon as it is stated specifically that the most elementary process of price determination must depend inter alia upon what people think is going to happen to prices in the future. The demand functions which Professor Cassel thinks enable US to dispense with any subjective elements must be conceived not merely as relating to prices which prevail now or which might prevail on present markets but also as relating to a whole series of prices which people expect to prevail in the future. It is obvious that what people expect to happen in the future is not susceptible of observation by purely behaviourist methods. Yet as Professor Knight and IV NATURE OF ECONOMIC GENERALISATIONS 89 others have shown it is absolutely essential to take such anticipations into account if we are to understand at all the mechanics of economic change. It is essential