• To a greater or lesser extent there goes on in every person a struggle between two forces: the longing for privacy and the urge to go places: the introversion, interest directed within oneself toward one's own inner life of vigorous thought and fancy; and extroversion, interest directed outward, toward the external world of people and tangible values.

    Vladimir Vladimirovich Nabokov, Fredson Bowers (1981). “Lectures on Russian literature”, Harcourt