This book deals with the problem of shadows and their impact on our visual experience. He juxtaposes the notions of shadows typical of modernity and those of the 18th century with the intention of taking advantage of the tension that is established between the two. It does not pretend to make, and does not do, a definition of shadows, but it pays attention both to its practice by painters and to its explanation by theoreticians, and shows that it is not a negative concept, a mere absence of light. Although it lacks a specific and permanent territory, it is not less active for that, nor does it stop contributing knowledge. Thinking about how the shadow could bring us knowledge entails the task of determining how and to what extent it does so.