He devoted particular attention to the moral problem, and to him we owe a Geschichte der Ethik (2 vols., Stuttgart 1888-89, 3rd ed. ibid. 1920), as well as a Lehrbuch der Psychologie (ibid. 1897, 4th ed. ibid. 1916) and a mediocre Kritik d. Idealismus (Leipzig 1920, posthumous). Close to Comte, he does not accept the cult of humanity and substitutes for it a “moral faith”: “The ideal within us and the faith in its progressive realization through us: this is the formula of the new religion of humanity” (Gesch. der Eth., p. 494). His metaphysics is a superficial materialistic monism: thought is a function of organic substance and matter and spirit coincide in a rather imaginary “psychic atom.”
BIBL.: Archiv. f. Gesch. der Philos., 27 (1914), entirely devoted to him; W. Ziegenfuss, s. V. in Philosophen-Lexikon, I, Berlin 1949, pp. 597-98 (with bibliography). Michele Federico Sciacca