Toward the close of the nineteenth century, a crisis of reason occurred, challenging positivist thought. Philosophy, psychology, and psychiatry were all asked to reexamine their conceptions of man and their scientific practices. The issue of subjectivity was explored not only through Freudian analysis, which was introduced at the end of the century, but also through other scientific methods, particularly French experimental psychology (Binet, Ribot, Richet) and hypnosis, which, despite its questionable scientific reliability, presented a new model of the mind and personality that was destined to be widely accepted beyond the sciences. These studies were at the forefront of scientific research. Luigi Pirandello engaged in both philosophical and scientific discourse, and his ideas and artistic works contributed to the deconstruction of traditional notions of self and identity, as seen in such works as One, No One, and One Hundred Thousand and Così è (se vi pare).

In this chapter, I review the history of psychological accounts of intelligence in the nineteenth and twentieth centuries. I open with an account of the thinking of Galton and Binet. Although Binet is often viewed as atheoretical, I show this not to be the case at all. I then discuss some of their successors, including Spearman, Thomson, Holzinger, Thurstone, Guilford, Guttman, Burt, Vernon, Cattell, Carroll, and Johnson and Bouchard.