Kasimir Twardowski studied philosophy under Brentano and Zimmermann in Vienna from 1885 to 1889. In 1892 his dissertation on Descartes, Idee und Perzeption, appeared and was followed in 1894 by his habilitation thesis, Zur Lehre vorn Inhalt and Gegenstand der Vorstellungen. He stayed in Vienna as a Privatdozent until 1895, when he was called to Lvov, where he was to exercise considerable influence in Polish philosophy. His influence in Poland was primarily due to his teaching activity, not to the few publications which he produced during the years in Lvov.¹ As a teacher he regarded his task as the advancement and application of the rigorous method which he had learned from Brentano, though he did not insist on promoting this or that particular doctrine. The result was in large measure the rise of the Polish school of logic, not to mention the impact which Twardowski had on phenomenologists such as Roman Ingarden and Leopold Blaustein. Here we are however concerned with the ideas which he had presented in his habilitation thesis, for Husserl's critical confrontation with these ideas was a crucial turning point in his philosophical development.