Environmental Politics, Volume: 26(4):561-579. doi.org/10.1080/09644016.2017.1327485    Introduction     ‘Together now!’ was the slogan used in the invitation to the Marrakesh Partnership for Global Climate Ac

Mind 130(520), 2021 Abstract The Bayesian maxim for rational learning could be described asconservative changefrom one probabilistic belief orcredencefunction to another in response to new information. ). But can this conservative-change maxim be extended to revising one’s credences in response to entertaining propositions or concepts of which one was previously unaware? The economists,) make a proposal in this spirit. Philosophers have adopted effectively the same rule: revision in response to growing awareness should not affect the relative probabilities of propositions in one’s ‘old’ epistemic state. The rule is compelling, but only under the assumptions that its advocates introduce. It is not a general requirement of rationality, or so we argue. We provide informal counterexamples. And we show that, when awareness grows, the boundary between one’s ‘old’ and ‘new’ epistemic commitments is blurred. Accordingly, there is no general notion of conservative change in this setting.