I have very diverse research interests. The following is a broad overview of them that gives you an impression of my main philosophical ideas and preferences.
Currently, I am working on a research project "Epistemology of the Multiverse", funded by the Netherlands Organization for Scientific Research (NWO) through a Veni grant. The project explores the prospects for empirically testing theories according to which the laws of nature and the constants vary across space-time or even across universes that together form a "multiverse". Easily accessible introductions to the themes of the projects can be found here and here. Often a "fine-tuning" for life of the laws and constants of nature is claimed to provide evidence that we live in a multiverse. I give an overview of that debate in my article on "Fine-tuning" for the Stanford Encyclopedia of Philosophy.
I am intrigued by the challenge to make sense of quantum theory. An excellent brief account of my published thoughts has been written by Richard Healey's in his SEP-entry "Quantum-Bayesian and Pragmatist Views of Quantum Theory", Section 5.1. My papers concerning the prospects for epistemic accounts of quantum states can be found here, here, here, here, and a paper concerning the compatibility of (so-called) non-local quantum correlations with relativity theory here. My monograph "Interpreting Quantum Theory -- A Therapeutic Approach" brings together all the different threads of my work on quantum theory until now. It has been reviewed for Erkenntnis by Florian Boge.
In addition, the significance of symmetries and symmetry breaking in physics have intrigued me, in particular how symmetries connect to questions of identity among physical states (here) and what it actually means for different types of symmetries to be spontaneously broken (here, here). I was guest editor of a special section on philosophical perspectives on particle physics after the Higgs discovery in Studies in History and Philosophy of Modern Physics, together with Dennis Lehmkuhl, see here.
Some of my work on quantum theory has a direct bearing on questions with a general relevance for philosophy of science, in particular concerning the nature of objective probabiliy and causation (here). Together with Koray Karaca and theoretical physicist Robert Harlander I wrote a paper on the notion "ad hoc hypothesis" and its application to methodological issues concerning the Higgs mechanism, in particular the violation of "naturalness" (here).
My work in epistemology focuses on problems of rational self-locating belief, a topic that has a bearing on diverse issues, from everyday contexts to the evaluation of cosmological theories. Two papers of mine in this field (here and here) explore the relevance of an epistemic agent's causal context and the appearance of anomalous causal powers according to some suggested accounts of self-locating belief.
I have recently started to work on energy and ethics. Human flourishing seems to require access to relatively cheap energy. But these days that energy comes mostly from burning fossil fuels, which in turn threatens human flourishing by contributing to climate change. I am particularly intrigued by the question whether we should invest a significant amount of resources in further development and deployment of nuclear energy in addition to increasingly harvesting surrounding energy flows such as solar and wind energy. At various occasions I have given talks on the ethics of nuclear energy deployment in the age of climate change. At the moment, I am working on an article on this topic together with my colleague Maarten Boudry.
To understand mathematics and mathematical activity, it is crucial to have a clear view of the functioning of mathematical language. I am tempted by Wittgenstein's idea that mathematical language has an essentially normative, rather than descriptive, mode of use. Whereas Wittgenstein applied this perspective on mathematics predominantly with an eye on applications of mathematics, I argue that it fits surprisingly well with the modern axiomatic approach to pure mathematics (here). As I see it, such a Wittgensteinian approach to mathematical language supports deflationary perspectives on mathematical truth and mathematical objects (in German). Inasmuch as a structuralist view of mathematical objects is compatible with such perspectives, I think that it can and should be extended to meta-mathematics (here).
As a PhD student in physics I co-authored three papers on high-temperature superconductivity and its relation to anti-ferromagnetism in a simple model of fermions on a lattice, the so-called Hubbard model (see here for the final installment of the series). This work is based on a renormalization group approach to the development of which my physics PhD supervisor Christof Wetterich made decisive contributions.