 First, in the realm of hedonic evaluation, there are marked divergences between the aggregate sums of in-the-moment pleasures and pains and ex post memories of pleasures and pains. For example, the remembered level of pain of a colonoscopy is well-predicted by the average of the worst momentary level of pain and the final level of pain; furthermore, the duration of the procedure has no measurable effect on ex post pain ratings (Redelmeier &amp; Kahneman 1996). What this means is that people’s after-the-fact summaries of their hedonic experiences are not simple integrals with respect to time of momentary hedonic tone. If the colonoscopy were functionally completed after minute 5, but arbitrarily prolonged for another 5 minutes so that the final level of pain was less at the end of minute 10 than at the end of minute 5, the patient would retrospectively evaluate the experience as less painful. This complicates accounts of well-being in terms of pleasure (for example, Bentham’s 1789/1961 hedonism) insofar as it raises the question whether the pleasure being measured is pleasure as experienced in the moment, or retrospectively: if, in the very act of aggregating pleasure, we change the way we evaluate it, this is a complication for hedonism and for some versions of utilitarianism. Since well-being is supposed to be a normative notion capable of guiding both individual actions and social policy, findings like these also call into question what, exactly, we ought to be seeking to maximize: pleasurable moments, or the overall retrospective evaluation of pleasure.