Franz Brentano was a philosopher and psychologist who is considered the founder of act psychology and had a lasting impact on his discipline. His students included Edmund Husserl and Carl Stumpf. The present work, which is regarded as one of the classics of psychology, consists of two parts: In the first part, Brentano approaches psychology as a science. The subjects of his investigations include the definition and methods of psychology. The second part is dedicated to psychological phenomena in general. Central to his discussion is the concept of "inner consciousness." The book originates from a time when psychology was still in its infancy as an independent discipline, as Brentano himself notes: "There are beginnings of a scientific psychology present, inconspicuous in themselves, but sure signs of the possibility of a fuller development.".