1. Time preference as a universal phenomenon: For Mises time preference was not an empirical regularity but a "definite categorical element...operative in every instance of action." Well, if time preference is seen as positive time preference, the claim that it is ever present in the decisions of each and every household may be true or false, and it is, therefore, an empirical proposition. On the other hand, since time preference may be large, small, zero, or even negative, we may assert that it is a universal characteristic of human action. If, when comparing present with future gratification, some individuals postpone consumption without the promise of a positive interest rate, their marginal rate of time preference is evidently zero. If, without receiving interest, they allocate their present and future availabilities in such a fashion that they may expect to consume equal amounts this year, next year, and in any future year, then their time preference in the schedule sense must be defined as being zero. But what the facts actually are remains an empirical question. People have different tastes, different incomes, different expectations of future income and needs, and different opportunities for trade-offs between present and future consumption.