This blogpost was authored by Dr Guido Bacciagaluppi from Utrecht University, The Netherlands. Dr Bacciagaluppi visited the University of Bristol in early 2025 to collaborate with Dr Karim Thebault on a Benjamin Meaker award.
I spent two extremely profitable months at Bristol working on philosophy of physics with Karim Thébault and others in the Department of Philosophy. When I came, I knew very well that Bristol was a powerhouse in both philosophy and foundations of physics (as well as in the philosophy of science), and had witnessed that in person two years ago when Bristol hosted Foundations2023 – that year’s edition of one of our most important conferences. When I saw the current and past Bristol contingent having their own group photo (something like 18 people!), I knew I had to be back for a longer period. And I will lavish praise on the Benjamin Meaker Distinguished Visiting Professorship programme, which provided me with just what I needed: excellent support, freedom to fashion my research stay as suited best, and very convenient accommodation – stunningly located in the heart of the university.

I walked everywhere, making a point at week-ends of exploring what I could of the city (a welcome change from the very flat surroundings I have become used to in the Netherlands). As a classical music lover, it was great to be 11 minutes’ walk from the Bristol Beacon (I timed it!), and even closer to the lunchtime recitals at the Victoria Rooms, and the welcoming University Church Choir who rehearse at St Paul’s, Clifton. I have further never been so close to my office in my life: had I been a squirrel, I could have covered the 15m between my bedroom and office windows in no time.

I mainly work in the philosophy of quantum mechanics and the history of the debates on its foundations, and scientifically my visit was very productive. My principal aim was to explore some new ideas with my host Karim Thébault about formulating quantum theory without the notion of state. (One inspiration comes from Heisenberg, who was antagonistic towards – Schrödinger’s – quantum states and preferred to see quantum theory as a theory about state-independent transition probabilities between values of physical quantities, and the state only as a mathematical artefact useful for calculating them.) We got on to a very good start (watch this space!) and in fact realised something that should have been obvious, that the project has rather deep connections with one of Karim’s own projects of conceptualising quantum theory in terms of open systems. We also managed to clarify our points of difference on the role played in quantum theory by decoherence, the spontaneous suppression of interference effects through interaction with the environment. These are points that are not clearly articulated in the literature and we plan to spell them out in a joint paper, which should be very useful for everyone interested in the topic. I also learned a lot in interaction with both Karim and James Ladyman on conceptual problems relating to quantum chemistry.
On the history side of things, I was very lucky to find not one but two BA International Fellows in the department, Jer Steeger and Noah Stemeroff, respectively working on Heisenberg and Pauli (among other things). I have a big ERC project in progress on Niels Bohr, trying to clarify his thought and its potential relevance to current debates in philosophy of physics, philosophy of biology and philosophy of science. I had numerous conversations that were very relevant for this project, especially with Jer about the disagreements between Bohr and Heisenberg on the gamma-ray microscope thought experiment.

I cannot list all the other things I managed to do, but for instance I had the opportunity to interact with the graduate students and do some teaching, and was extremely impressed by their quality and preparation. I also had the opportunity to give a seminar on work of mine in the philosophy of probability that I was keen to advertise and for which I found a very appreciative audience.
My visit was very well timed also because it overlapped with another Benjamin Meaker visiting professor in our field, Dean Rickles from the University of Sydney (an erstwhile colleague from my own time there). Karim, Dean and I co-organised a one-day workshop shortly before I left again for my home university of Utrecht, entitled Quantum Investigations, with talks from Dean, Bristolians and co-workers, three other members of my ERC project, and myself. The line-up of topics worked extremely well, and the workshop rounded off very appropriately two very good months. I hope to be back soon, because professionally and personally the environment at Bristol has been perfect!













