I see no means by which such a comparison [between the motives of one man and those of another] can be accomplished. The susceptibility of one mind may, for what we know, be a thousand times greater than that of another. But, provided that the susceptibility was different in a like ratio in all directions, we should never be able to discover the difference. Every mind is thus inscrutable to every other mind, and no common denominator of feelings seems to be possible.... But the motive in one mind is weighed only against other motives in the same mind, never against the motives in other minds. Each person is to other persons a portion of the outside world--the _non-ego_ as the metaphysicians call it. Thus the motives in the mind of A may give rise to phenomena which may be represented by motives in the mind of B; but between A and B there is a gulf. Hence the weighing of motives must always be confined to the bosom of the individual. This question as to the homogeneity and communicability of emotional states in different men is one fundamental to any value theory which starts with individual feelings or desires as elements--and, indeed, from a somewhat different viewpoint, is fundamental to all value theory. Value, as a concrete quantity of desire or feeling, embodied in a given good at a given time, regardless of who is purchaser and who is seller, can exist only if feelings and desires are homogeneous and can interact--even in Wieser's ideal society, where the complication of differences in wealth does not obtain. And value must have some very different meaning unless this assumption be held. In illustration of this, I wish to quote further from Jevons. Jevons finds for value[50] three distinct meanings, for each of which he employs both a "popular" and a "scientific" name: (1) value in use ("popular" name) = total utility ("scientific" name); (2) esteem, or urgency of desire ("popular" name) = final degree of utility ("scientific" name); (3) purchasing power ("popular" name) = ratio of exchange ("scientific" name). Now the first two of these are purely subjective, individual facts, varying as to their quantities for each individual. The only one that can have social meaning is the third, and that, as Jevons explicitly states, is a numerical ratio, an abstract number.[51] This is brought out very clearly when he discusses the question of the concrete dimensions of these three quantities. Total utility has dimensions, and so has final utility, but ratio of exchange, which he considers the precise scientific equivalent for the popular term, purchasing power, has no dimension at all. Its dimension is zero. Finding these ambiguities in the word value, Jevons proposes to abandon it altogether, and to use instead either of the three expressions discussed, depending on which sense of the