Knowledge falsification is the deliberate misrepresentation of what one knows under perceived social pressures. The term was coined by Timur Kuran in his book Private Truths, Public Lies: The Social Consequences of Preference Falsification. According to Kuran’s analysis of preference falsification, knowledge falsification is usually undertaken to signal a preference that differs from one’s private preference, in other words, to support preference falsification. Successful misrepresentation of one's private preferences requires hiding the knowledge on which they rest. Thus, people engage in preference falsification, or bolster it, by misrepresenting their information, interpretations, and understanding. Such misrepresentation is a response to perceived social, economic, and political pressures. The perceived pressures could be partly, if not fully, imaginary. The pressures may be rooted in speech controls imposed by a state and enforced through state-enforced punishments. But, as with preference falsification, knowledge falsification need not be a response solely, or even mainly, to pressures from the state or some other organized political entity. The source of pressures is partly individuals seeking to display conformity to an agenda that appears politically popular. In any given context, knowledge falsification may end abruptly, through a self-reinforcing shift in public opinion. Among the effects of knowledge falsification is the distortion, corruption, and impoverishment of knowledge in the public domain. Society is denied exposure to what is believed to be true, and it gets exposed instead to information that its bearers consider false. A further effect is widespread ignorance about policy failures and about the potential advantages of reforms. Knowledge falsification can also bring intellectual narrowness and ossification, harming innovation. Yet another possible consequence is the persistence of policies, customs, norms, fashions, and institutions that are widely disliked.