A noema is the object, or content, of a thought. But can we see the content of thought? Yes. Throughout history we’ve made many pictures of these ‘thought-objects’, often calling them ‘diagrams’. But the story of the diagram is quite different from the traditional history of art. Because they escape easy categorization, diagrams are everywhere, in corporate boardrooms and schools, in sports, dance and warfare, in art, philosophy, science, magic and everything in between. Instead of likeness, the diagram pursues liveliness; instead of making images, it stimulates the imagination.