This introduction presents an overview of the key concepts discussed in the subsequent chapters of this book. The book offers a different definition of the Renaissance and of Piero's place in it. It provides a variety of fifteenth-century authors—painters and non-painters—who claim a special relationship between art and the world in which it was made. This book argues that part of the world people see in Piero's paintings consists of his world. It is sometimes almost as if Piero could not help to have the place where he was painting to enter the picture. Piero's understanding of perspective, which, the book argue, cultivates the illusion that his painting depicts a scene discovered rather than made or invented. The book focuses on the time of painting: The world that was there when Piero was painting and that became fixed inside Piero's pictures.