Why zero temporal discounting *within* a life is less plausible than across generations

For an individual there is both cardinal Benthamite utilitarianism (“utils”) and preference utilitarianism.  The two sometimes conflict (would you take a pill that gave you joy when you saw suffering?), and a plausible consequentialist theory attaches some weight to both.

Most of the arguments for zero discounting of utility apply to the cardinal measure.  Don’t put off going to the dentist just because you don’t like pain — when the pain finally arrives, it will be no less real.

But now shift your attention to the preference utilitarianism.  Let’s say a person had a strong preference that “the Knicks win an NBA title in 2022,” deciding that it isn’t nearly good enough for the Knicks to win that title in 2030.  That is a kind of positive time preference.  Arguably it is ungrounded and irrational, but that isn’t quite grounds for dismissing it.  Preference utilitarianism simply counts the preference and whether it is satisfied.  You might as well argue it is irrational to care about the Knicks in the first place, never mind 2022 vs. 2030.  And indeed it is, just like so many other of our preferences do not really admit of defense or justification in external terms.

And thus, through the medium of preference satisfaction utilitarianism, we cannot altogether dismiss positive time preference for the individual.

When considering trade-offs of utilities across the generations, there are Benthamite comparisons but there is no meaningful preference utilitarianism, since there are different persons at stake.  That leaves us with one fewer argument for positive time preference in the intergenerational case.