What does it mean to think with images? There is a well-established tradition of studying thought processes through the nature of language, and we know much more about thinking with language than about thinking with images. Piotr Kozak takes an important step towards rectifying this position. Presenting a unified theory of different types of images, such as diagrams, maps, technical drawings and photographs, Kozak argues that images provide a genuine and autonomous form of content and knowledge. In contrast to the propositional view of thinking and resemblance-based accounts, he puts forward a measurement-theoretic account of images as operations that exemplify measures, revealing the outcomes of measurement operations performed on a depicted situation. Bringing together insights from philosophy of science, picture-theory, cognitive science and cognitive psychology, this book demonstrates that we can only understand what an image is if we truly understand the role they play in our thought processes, challenging the prevailing view that the utility of images is only instrumental and cognitively inferior.