After a long hiatus, our project’s research seminar at the University of Warsaw starts again in October 2022. As in the previous years, the seminar is devoted to philosophical, conceptual, and formal issues in the context of formal truth theories and implicit commitments of foundational theories. Although the talks take place in person, we also welcome online attendance. We plan to have meetings twice a month during the semester.

We have the following permanent link to seminar meetings:

If you wish to be put on the mailing list, please contact Mateusz Łełyk (mlelyk(at)

Upcoming talks

13.05.2024 Tim Button (UCL), Implicit commitments of “implicit commitments”: the ω-rule and second-order internal categoricity.


I accept Peano Arithmetic. In doing so, I think I am probably implicitly committed to Con_{PA}; to the Local Reflection principle; to stronger reflection principles still… 

But my aim in this talk is not to probe the frontiers of these implicit commitments. Instead, I want to consider the implicit commitments of (common) arguments for the claim that we have such implicit commitments. I argue that these arguments are implicitly committed to both: 
(1) the soundness of the ω-rule, and 
(2) the acceptability of second-order induction with an (impredicative comprehension schema)

These commit us (respectively) to both the intra-subjective and inter-subjective determinacy of the natural numbers.