In this Very Short Introduction Duncan Pritchard explores both the advantages of scepticism, in challenging outdated notions, and also how it can have unhelpful social consequences, in generating distrust. He considers the role of scepticism at the source of contemporary social and political movements such as climate change denial, post-truth politics, and fake news. Pritchard also examines the philosophical arguments for a radical form of scepticism which maintains that knowledge is impossible, and explores some of the main responses to these arguments. Finally, he considers the part scepticism might play in applying better thinking and learning to achieve a more meaningful life.