In 1881 he obtained his doctorate with the dissertation Untersuchungen über das Causalproblem auf dem Boden einer Kritik der einschlägigen Lehren J. St. Mills ("Investigations concerning the problem of causality on the basis of a critique of the relevant doctrines of John Stuart Mill").
[3] In 1885 he obtained his habilitation as Privatdozent in Strasburg with Grundzüge einer Theorie der mathematischen und nicht-mathematischen Grenzbegriffe.
[7] Kerry exercised an influence not just within the circle of Brentano, especially on Alois Höfler (for the concept "psychical labor"), Edmund Husserl (in the Philosophy of Arithmetic),[3] and Kazimierz Twardowski,[8] but also on Gottlob Frege.
Kerry (in particular in his fourth article) criticized Frege for having confused concept and object in his Die Grundlagen der Arithmetik and in Begriffsschrift.
[10] Frege responded to a number of aspects of this critique in 1892 with the paper "Begriff und Gegenstand" ("Concept and Object").