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The Forum is open to everyone, including students, visitors, and faculty members from all departments and institutes!

The 60 minute lecture is followed by a 10 minute break and a 30-60 minute discussion. The language of presentation is English or Hungarian.

The scope of the Forum includes all aspects of theoretical philosophy, including:

  • logic and philosophy of formal sciences
  • philosophy of science
  • modern metaphysics
  • epistemology
  • philosophy of language
  • problems in history of philosophy and history of science, relevant to the above topics
  • particular issues in natural and social sciences, important for the discourses in the main scope of the Forum.


3 April (Wednesday) 5:00 PM  Room 226
Elias Zafiris
Department of Logic, Institute of Philosophy, Eötvös University
on leave from
Institute of Mathematics, National University of Athens
The Role of Topology in the Interpretation of Quantum Event Structures
One of the deepest insights of  quantum  theory  is that  although  the totality  of  all experimental/empirical  facts  can  only  be represented globally  as a non-Boolean event structure,  the  acquisition  of  every  single  fact  depends  on  a  local Boolean frame. This is tied with the particular formalization of the notion of an observable in quantum theory, namely a self-adjoint operator. More precisely, each self-adjoint operator has associated with it a Boolean frame which is identified with the complete Boolean algebra of projection operators belonging to its spectral decomposition. In this way, complete Boolean algebras of projection operators can be considered as local Boolean logical recognition frames for the individuation of events. We claim that the current set-theoretic models of quantum event structures underscore the functional role of interconnected families of local Boolean frames in the global formation of quantum structures. We propose to remedy this deficiency in terms of a local-to-global sheaf-theoretic model, where the global information of a quantum algebra can be topologically localized to covering systems of local Boolean frames, and inversely induced by them via gluing. We discuss the application of this topological scheme in relation to quantum non-separability.

10 April (Wednesday) 5:00 PM  Room 226
Jenő Pöntör
Institute of Philosophy, Eötvös University, Budapest
Mi a baj a nemreduktív fizikalizmussal?
(What's wrong with nonreductive physicalism?)
Előadásomban először felvázolom a kortárs fizikalizmus három fő formájának – az antirealista, a reduktív, illetve a nemreduktív fizikalizmusnak – legfontosabb állításait, majd a mellett érvelek, hogy az antirealista és reduktív fizikalista elméletek empirikusan jól megalapozott hipotézisek, ezzel szemben a nemreduktív fizikalizmus elvileg igazolhatatlan tézis.

17 April (Wednesday) 5:00 PM  Room 226
Attila Molnár
Department of Logic, Institute of Philosophy
Eötvös University, Budapest
Mass and Modality
The Logic and Theory of Relativity group lead by Andréka, H. and Németi, I. developed several axiom systems for relativity theory to investigate it within mathematical logic.

One of the simplest and most commonly used axiom system is an axiom system of kinematics, the so-called SpecRel. Although this axiom system is very simple, it implies all the main predictions (theorems) of special relativity theory. However, as it is proposed by the group in many articles, sometimes the classical first-order logic framework of SpecRel does not seem to be sufficient to give back the appropriate physical meaning. For example, the main axiom of SpecRel, the axiom which is about the possibility of sending out light signals, states that there could be a photon which crosses certain points. This "could be" indicates some kind of notion of possibility, which is barely accessible from a classical first-order logic.

This problem becomes more serious when we try to expand the system SpecRel by certain dynamical axioms (to get SpecRelDyn). For example, we would like to postulate that for every observer, everywhere, any kind of possible collision is realizable. It is worth to investigate this type of axioms, because this way leads to an experimental understanding of the notion of possibility.

We will investigate axiom systems of special relativity based on modal logic, which is the standard tool for formally handle dynamical notions – such as performing a (thought-) experiment, for instance "send out a light signal" or "realize a collision".

Our axiom systems will be built with the following goals:
- Give a plausible but formal notion of possibility/experimentation based on the informal explanations of the classical SpecRel and SpecRelDyn.
- Save the theorems and the ideas of their proofs from SpecRel and SpecRelDyn.
- Show that in a modal framework the mass can be explicitly defined essentially in the language of kinematics. This can be viewed as the formal interpretation of the operational definition of mass.

24 April (Wednesday) 5:00 PM  Room 226
Péter Mekis
Department of Logic, Institute of Philosophy
Eötvös University, Budapest
Thought Experiments as Semantic Arguments
In the last couple of decades, there has been an intensive debate concerning the epistemological status of thought experiments. Whether in science or in philosophy, these tools of investigation apparently provide important new knowledge in spite of being entirely a priori, and thus they pose a serious challenge to empiricism. One of the crucial questions of this debate is:  Are thought experiments indispensable, or are they reducible to ordinary arguments within a given theory?

One characteristic point of view regarding this question is that the phenomenon of thought experiments does actually falsify empiricism, providing quasi-perceptional, yet a priori knowledge. Thought experiments are experimental in nature; the only difference between them and actual experiments is that the objects of observation are abstract entities, instead of physical ones.This view rules out the possibility that thought experiments could be reduced to arguments. Another extreme is the reductionist view, according to which a thought experiment is an argument in a fictional disguise, which can be left out without any theoretical loss.

My suggestion is that a great deal of thought experiments function as semantic arguments concerning the satisfiability or categoricity of scientific or philosophical theories. They are not experimental in nature; but they are not arguments within a (scientific or philosophical) theory either. Rather, these arguments serve as tests for theory choice. Being about (rather than part of) theories, they differ genuinely from the deductive arguments which prove the theories' facts. But, on the other hand, no appeal to quasi-perceptional knowledge is required to account for their correctness.