One widespread argument against the efficacy of subjective well-being as a measure of well-being is the adaptation problem as formulated by Sen and Nussbaum: the phenomenon that people may adapt to deprivation and find satisfaction or happiness in objectively bad circumstances. It is not generally noticed that there are two distinct arguments for why the phenomenon of adaptation is a problem for subjective well-being as a measure of well-being. The Axiological Adaptation Argument is a counter-example to theories of well-being that (...) rely on mental states. The Epistemic Adaptation Argument illustrates that levels of happiness or satisfaction cannot be measured well when people have adapted. I argue that the most serious threat to subjective well-being measures is not the Axiological Argument, but the Epistemic Argument. I reflect on the implications the epistemic problem has for the empirical literature in general, and for research on the phenomenon of adaptation in particular. (shrink)