Idealization is a fundamental feature of human thought. We build simplified models in our scientific research and utopias in our political imaginations. Concepts like belief, desire, reason, and justice are bound up with idealizations and ideals. Life is a constant adjustment between the models we make and the realities we encounter. In idealizing, we proceed "as if" our representations were true, while knowing they are not. This is not a dangerous or distracting occupation, Kwame Anthony Appiah shows. Our best chance of understanding nature, society, and ourselves is to open our minds to a plurality of imperfect depictions that together allow us to manage and interpret our world.The philosopher Hans Vaihinger first delineated the "as if" impulse at the turn of the twentieth century, drawing on Kant, who argued that rational agency required us to act as if we were free. Appiah extends this strategy to examples across philosophy and the human and natural sciences. In a broad range of activities, we have some notion of the truth yet continue with theories that we recognize are, strictly speaking, false. From this vantage point, Appiah demonstrates that a picture one knows to be unreal can be a vehicle for accessing reality. As If explores how strategic untruth plays a critical role in far-flung areas of inquiry: decision theory, psychology, natural science, and political philosophy. A polymath who writes with mainstream clarity, Appiah defends the centrality of the imagination not just in the arts but in science, morality, and everyday life.