Concerning Frege’s philosophy of mathematics, Schirn has more recently focused and published on the introduction of logical objects by means of second-order abstraction principles, their logical, semantic and epistemological nature, the problem of referential indeterminacy of abstract singular terms to which those principles give rise in a Fregean context, the foundations of real analysis and of geometry and last but not least on some aspects of neo-logicism. In a series of articles co-authored by Karl-Georg Niebergall, Niebergall and Schirn presented Hilbert’s finitist proof-theoretic approach in a new light by paying close attention to the development of his metamathematical work in the period 1922-1939 and by using the logical resources of modern proof theory. One important result of their published work is that Peano Arithmetic proves its own consistency indirectly in one step and that recursively enumerable extensions of QF-IA (QF = quantifier free — IA = induction axiom) likewise prove their own consistency indirectly in one step. Schirn and Niebergall are also known for their analysis of Hilbert’s extensions of the finitist point of view in the light of Gödel’s incompleteness theorems and their attempted refutation of W. W. Tait’s widely accepted thesis that all finitist reasoning is primitive recursive (W.W. Tait, ‘Finitism’, Journal of Philosophy 78, 524-46). Webpage of the LMU Philosophy Department: http://www.philosophie.uni-muenchen.de/lehreinheiten/wissenschaftstheorie/personen/ehemalige/schirn/index.html which also contains an extensive CV to corroborate all of the information found here https://web.archive.org/web/20150620131641/http://www.philosophie.uni-muenchen.de/lehreinheiten/wissenschaftstheorie/personen/ehemalige/schirn/cv.pdf  A condensed CV of Matthias Schirn including a list of selected publications (up to 2008) can be found in The International Directory of Logicians. Who’s Who in Logic, edited by Dov M. Gabbay and John Woods, College Publications, London 2009, pp. 306–308.  http://blog.nus.edu.sg/philo/2013/01/16/the-true-and-what-might-be-the-truth-about-is-true-a-critical-examination-of-freges-views-by-matthias-schirn-24-jan/