Kazimierz Twardowski was born in Vienna,¹ where from 1885 to 1889 he studied under Brentano and met the Brentanians of the period.² In 1891 he submitted his thesis Idee and Perception. Eine erkenntnistheoretische Untersuchung aus Descartes, but since Brentano was only a Privatdozent, discussed it with Robert Zimmermann, one of Bolzano's pupils. After graduating he went to Leipzig for a short period to join Wundt's circle of students, and then moved to Munich to study under Stumpf. In 1894 he returned Vienna, where he wrote his major work, Zur Lehre vom Inhalt and Gegenstand der Vorstellungen. The following year he moved to Lvov, where he taught until 1930. In 1898 he published Wyobrazenia i pojęcia [Images and concepts] as both an extension and a simplified version of his theory. A modified German version of the book came out in 1902 bearing the title Über begriffliche Vorstellungen and a further Polish verson O istoicie pojęć [On the nature of concepts] in 1923.