, hậu quả có đối ứng trong thực tế không phải là ngay lập tức nhận thấy rõ là các đối tác của ban đầu định đề. Nó là một công cụ để "lắc" tất cả các tác động của giả định cho. Cấp tương ứng của các giả định ban đầu của nó và các sự kiện, | VI THE SIGNIFICANCE OF ECONOMIC SCIENCE 139 faction which the Baker gets by receiving it. That comparison is a comparison of an entirely different nature. It is a comparison which is never needed in the theory of equilibrium and which is never implied by the assumptions of that theory. It is a comparison which necessarily falls outside the scope of any positive science. To state that A s preference stands above B s in order of importance is entirely different from stating that A prefers n to m and B prefers n and m in a different order. It involves an element of conventional valuation. Hence it is essentially normative. It has no place in pure science. If this is still obscure the following considerations should be decisive. Suppose that a difference of opinion were to arise about A s preferences. Suppose that I thought that at certain prices he preferred n to m and you thought that at the same prices he preferred m to n. It would be easy to settle our differences in a purely scientific manner. Either we could ask A to tell us. Or if we refused to believe that introspection on A s part was possible we could expose him to the stimuli in question and observe his behaviour. Either test would be such as to provide the basis for a settlement of the difference of opinion. But suppose that we differed about the satisfaction derived by A from an income of 1 000. and the satisfaction derived by B from an income of twice that magnitude. Asking them would provide no solution. Supposing they differed. A might urge that he had more satisfaction than B at the margin. While B might urge that on the contrary he had more satisfaction than A. We do not need to be slavish behaviourists to realise that here is no scientific evidence. There is no means of testing the magnitude of 140 SIGNIFICANCE OF ECONOMIC SCIENCE CH. A s satisfaction as compared with B s. If we tested the state of their blood-streams that would be a test of blood not satisfaction. Introspection does not enable A to