books, and "social" intercourse, the shares of income we expend upon them or the marginal prices we are content to pay express the original strength of separate and unmodified extra-market interests? On the contrary we have paid in the past what we have had to pay, what we have deemed just and reasonable, what we have been willing experimentally to hazard upon the possibility of the outlay's proving to have been worth while. In these twilight-zones of indetermination, cost as well as other factors of supply have had their opportunity. Shall we nevertheless insist that our "demands" are _ideally_ fixed, even though in fallible human fact they are more or less indistinct, yielding and modifiable? On the contrary they are "in principle and for the most part" indeterminate and expectant of suggested experimental shaping from the supply side of the market. It is less in theory than in fact that they have a salutary tendency (none too dependable) toward rigidity. CONCLUSION Sec. 19. The argument may now be summarily reviewed. I. How are we to understand the acquisition, by an individual, of what are called new economic needs and interests? Except by a fairly obvious fallacy of retrospection we cannot regard this phenomenon as a mere arousal of so-called latent or implicit desires. New products and new means of production afford "satisfactions" and bring about objective results which are unimaginable and therefore unpredictable, in any descriptive fashion, in advance. In a realistic or empirical view of the matter, these constitute genuinely new developments of personality and of social function, not mere unfoldings of a preformed logical or vital system. "Human nature" is modifiable and economic choice and action are factors in this indivisible process (Sec.Sec. 2-4). Now "logically" it would seem clear that unless a new commodity is an object of desire it will not be made or paid for. On the other hand, with equal "logic," a _new_ commodity, it would seem, _cannot_ be an object of desire because all desire must be for what we already know. We seem confronted with a complete _impasse_ (Sec. 5). But the _impasse_ is conceptual only. We have simply to acknowledge the patent fact of our recognition of the new as novel and our interest in the new in its outstanding character of novelty. We need only express and interpret this fact, instead of fancying ourselves bound to explain it away. It is an interest not less genuine and significant in economic experience than elsewhere (Sec.Sec. 6, 7). Its importance lies in the fact that it obliges us to regard what is called economic choice not as a balancing of utilities, marginal or otherwise, but as a process of "constructive comparison." The new commodity and its purchase price are in reality symbols for alternatively possible systems of life and action. Can the old be relinquished for the new? Before this question is answered each system