Photography matters, writes Jerry Thompson, because of how it works -- not only as an artistic medium but also as a way of knowing. It matters because how we understand what photography is and how it works tell us something about how we understand anything. With these provocative observations, Thompson begins a wide-ranging and lucid meditation on why photography is unique among the picture-making arts. Thompson, a working photographer for forty years, constructs an argument that moves with natural logic from Thomas Pynchon (and why we read him for his vision and not his command of miscellaneous facts) to Jonathan Swift to Plato to Emily Dickinson (who wrote "Tell all the Truth but tell it slant") to detailed readings of photographs by Eugene Atget, Garry Winogrand, Marcia Due, Walker Evans, and Robert Frank. He questions Susan Sontag's assertion in On Photography that "nobody" can any longer imagine literate, authoritative, or transcendent photographs. He considers the money-fueled expansion of the market for photography, and he compares ambitious "meant-for-the-wall" photographs with smaller, quieter works. Forcefully and persuasively, Thompson argues for photography as a medium concerned with understanding the world we live in -- a medium whose business is not constructing fantasies pleasing to the eye or imagination but describing the world in the toughest and deepest way.