 As a way of understanding Galileo’s accomplishments, it is useful to see him as being interested in finding a unified theory of matter—a mathematical theory of the material stuff that constitutes the whole of the cosmos. Perhaps he did not realize that this was his grand project until the time he actually wrote the Two New Sciences in the mid-1630s. Despite working on problems of the nature of matter from 1590 onwards, he could not have written his final work much earlier than 1638; certainly not before the Starry Messenger of 1610, and probably not before the Dialogue Concerning the Two Chief World Systems of 1632. He had thought deeply about the nature of matter before 1610 and had tried to work out how best to describe matter, but before 1632, he did not have the theory and evidence he needed to support his claims about a unified, singular matter. The idea of unified matter theory had to wait for the establishment of principles of matter’s motion on a moving Earth. And this he did not accomplish until the Dialogue.