For the first time, Whitehead's readers will be able to see the development of his philosophy during the crucial period between the publication of Science and the Modern World and his delivery of the Gifford lectures that would become Process and Reality, as he tests his theories in a classroom setting. These student notes provide the long-missing window into critical developments in Whitehead’s thinking during this time. They challenge longstanding speculations about when exactly Whitehead developed some of his most famous metaphysical concepts, and how those concepts are to be properly interpreted against the wider backdrop of his life and thought.