Nicola Abbagnano, born in Salerno, was the chief exponent of Italian existentialism, which he defined as a militant and rational "philosophy of the possible." Originally a pupil of Antonio Aliotta at the University of Naples, Abbagnano began teaching at the University of Turin in 1936, where he also for years had been coediting the influential Rivista di filosofia. Practically since his first book, Le sorgenti irrazionali del pensiero (Naples, 1923), Abbagnano had been advocating a change of philosophical horizon suitable to the problematic nature of human life. This advocacy is reflected in a notable series of historical studies, culminating in the monumental three-volume work Storia della filosofia (Turin, 1946–1950; 2nd ed., 1963).

Reacting against the prevailing neo-Hegelianism of Benedetto Croce and Giovanni Gentile in Italy, Abbagnano was influenced, in turn, by Edmund Husserl's phenomenology and, later, by Søren Kierkegaard, Martin Heidegger, and Karl Jaspers; but he revealed...