§ 17. We have held constructive comparison in its economic phase to be a reciprocal evaluating of the "salient members" of two budgets. The respective budgets in such a case express in the outcome (1) the plane of life to which one is to move and (2) the plane one is forsaking. It was the salient member of the former that presented the problem at the outset. In the course of the process its associates were _gathered about_ it in their due proportions and perspective. The salient member of the latter (i.e., whatever the purchase is to oblige one to do without), it was the business of constructive comparison to _single out_ from among its associates and designate for sacrifice. In any case at all departing from the type of substitution pure and simple, the commodities sacrificed will come to have a certain "value in exchange" that clearly is a new fact, a new judgment, in experience. This value in exchange, this "subjective" or "personal" exchange value, may fittingly be termed a "value for transition." The transition once made, the exchange once concluded, I shall deem the motor-car, for example, that I have _not_ bought to replace one used-up, to be worth less than the piano I _have_ bought instead. This indeed (in no disparaging sense) is a tautology. But does this lesser relative value equal or exceed or fall short of the value the car would have had if no question of a piano had been raised at all and I had bought it in replacement of the old one as a matter of course? How can one say? The question seems unmeaning, for the levels of value referred to are different and discontinuous and the magnitudes belong to different orders. In a word, because a "value for transition" marks a resolve and succinctly describes an act, it cannot be broken in two and expressed as an equating of two magnitudes independently definable apart from the relation. The motor-car _had_ its value as a member of the old system--the piano _has_ its value as a member of the new. "The piano is worth more than the car"; "the car is worth less than the piano"--these are the prospective and retrospective views across a gulf that separates two "specious presents," not judgments of static inequality in terms of a common measure.