This research is devoted to several aims:

I. The first stage of work is concerned with Nietzsche’s philosophy, with regard to his view of the self/I. The research is particularly aimed at contextualizing Nietzsche’s rejection of the absolute value of the ego within the studies in physiology and psychology of the 19th century. This investigation contributes to the wider research field devoted to the scientific sources of Nietzsche’s thought, that in the last decades showed that, with regard to several fundamental problems, Nietzsche’s philosophical view is strictly connected with previous scientific views of his time. This is the case of his view of the self, whose ground can be found in the debate on scientific psychology, and in works of scientist and thinkers such as F. Lange and E. Mach, whose books Nietzsche read and sometimes quoted.

II. The second stage of the research is devoted to the ground of Nietzsche’s view of the self, i.e. the 19th century debate in psychology. The investigation is first concerned with the authors who stressed the importance of physiology for psychology (H. Helmholtz, J. Müller, and G. Fechner), and then with those who, by making reference to these authors, led the studies in psychology to a new stage (F. Brentano, F. Lange and E. Mach). The development of psychology from Helmholtz to Mach represents the shift from a metaphysical view of the soul to a scientific one. I.e., after Brentano, Lange and particularly Mach, we can talk about a “psychology without a soul”, and look at the “psychical unity” – the I – as a mere fictional concept, which cannot be found as a material entity in the brain. This outcome clearly involves some important remarks on the mind-body problem, that has been taken into account and developed by several 20th century philosophers and scientists, and nowadays is still a topic of heated debate.

III. The final stage of the project concerns another author who dealt with some fundamental questions of 19th century psychology, and developed them on both the scientific and the philosophical plane: William James. I will particularly focus on the last stage of James’ thought, i.e. his radical empiricism and his view on consciousness and the self (“Does “Consciousness” exist?”, 1912). James’ radical empiricism is in fact grounded on Mach’s empirio-criticism and on what Bertrand Russell called his “neutral monism” (“The analysis of Mind”, 1921), i.e. the view of a parallelism between the physical and the psychical (Mach, “The analysis of Sensations”, 1886). According to this view, we cannot talk about a mind-body problem from a dualistic perspective, since “mind” and “body” are only an interpretation in psychical and physical terms of a “neutral” reality. Our investigation on the self, I, consciousness etc. must therefore be carried out with no reference to substance concepts.