This second volume in the critical edition reproduces more than 170 lectures delivered by Alfred North Whitehead at Harvard during his second and third years. For the first time, readers will be able to see the development of Whitehead’s 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, as well as how those concepts are to be properly interpreted against the wider backdrop of his life and thought. Also included is a transcript of the only known lecture Whitehead delivered on the topic of ethics, two mid-year exams given to his students, and nearly 2,000 footnotes that provide additional context for the lectures and alternative student accounts of key passages.