This book is a follow-up to the book Tracing the Emergence of Psychology, 1520-1750: A Sophisticated Intruder to Philosophy (Springer 2020). In contrast, this new book covers the period 1750-1900. Whereas the previous book focused on how psychology intervened in philosophy and theology, the perspective now is how philosophy and psychology tried to free themselves from each other. Kant’s critical project formed an important start on this. Nevertheless, this was a struggle during the whole period, with a culmination at the end of the 19th century. When experimental psychology was established in Leipzig, psychology became regarded as an independent science. Another aspect of this new project is to pursue how experimental psychology ended up with music and culture as important factors. These are highly related to the role of sensation in psychology, which influenced how Baumgarten turned the psychological project into aesthetics in 1750. Thus, psychology in dialogue with music and aesthetics forms the red thread in this book. This book targets all interested in the history of psychology.