We are all apt to alter our beliefs and even our principles to suit the prevailing winds. Examples abound in public life (think of the politician who bases an election campaign on the need to address the budget emergency represented by a deficit, only to be indifferent to an even larger deficit once in office), but we are all subject to similar reversals. We often accuse one another of hypocrisy when these kinds of reversals occur. Sometimes the accusation is justified. In this paper, however, I will argue that in many such cases, we don’t manifest hypocrisy, even if our change of mind is not in response to new evidence. Marshalling evidence from psychology and evolutionary theory, I will suggest that we are designed to update our beliefs in response to social signals: as these signals change, we change our minds, often without even noticing.