Imaginable Impossibilities and Thought Experiments

A new online seminar on the Oxford Calculators

Dear colleagues, 

Our Calculatores Project, in collaboration with Sylvain Roudaut (University of Stockholm), is very happy to announce a new series of online seminars dedicated to the Oxford Calculators and their Tradition

All seminars will take place on Zoom, please contact the organizers if you are interested in participating, or subscribe via our website page:

The first seminar will be on November 15th, 3-5 pm (CET), and will feature two talks by Cecilia Trifogli and Marek Gensler, chaired by Sylvain Roudaut. Please find all details here:

The following seminars will take place monthly from November 2022 to May 2023. The list of speakers includes: Guido Alt; Fabrizio Bigotti; Irene Binini; Luca Burzelli; Graziana Ciola;Daniel Di Liscia; Michale Dunne; Marek Gensler; Pree Jareonsettasin; Elzbieta Jung; Severin Kitanov; Monika Michałowska; Andrea Nannini; Robert Podkonski; Sylvain Roudaut; Cecilia Trifogli; Sara Uckelman (tbc).

Please find other details on the series on our website

We hope this series can be of interest for many of you. Please feel free to contact me or Sylvain ( if you have any question or if you’d like to have the Zoom link.

Our first meeting:

Tuesday, November 15th 2022.

on Zoom (15.00-17.00 CET)
The Calculators’ predecessors

Marek Gensler (University of Lodz): “Walter Burley’s Opinions on Change in hisTractatus primus” 

Tractatus primus was composed by Burley in Paris in 1319 or 1320. The work has two parts: the first one is an analysis of four philosophical problems related to Eucharistic transubstantiation, the other is a report of the debate on those issues with his fellow scholars from the faculty of theology. The questions that make up the treatise address the following issues: whether a quality can produce a substantial change, whether an agent must be active in the moment of introducing the substantial form into matter, whether celestial, elementary and animal heat belong to the same species, whether opposing forms, such as blackness and whiteness, belong to the same species, are somehow related to the problem of change and its first and last moment. The changes he analyzes belong to the categories of substantial, elementary and qualitative change. 

Cecilia Trifogli (University of Oxford): “Thomas Wylton and Walter Burley on the Ceasing of an Instant of Time “

The topic of my talk is a remarkable application of the general theory of incipit and desinit to the treatment of a classical problem in Aristotle’s theory of time. In Physics IV.10 Aristotle presents a puzzle about the now (i.e., the present instant of time). It is asked whether the now is always different or always the same, and it is argued that neither of these two options is admissible. Relevant for my talk is the part of the puzzle that deals with the alternative that the now is always different. This can be reformulated as a problem about the ceasing of an instant of time, and specifically about the temporal measure of this ceasing: when does an instant cease to exist? Aristotle’s puzzle shows that there is no satisfactory answer to this question. On the contrary, Wylton and Burley maintain that the question can be answered and the essential conceptual tool that provides such an answer is the logic of incipit and desinit. In my talk I will present the solutions proposed by the two philosophers and compare them. Although they are different, I will point out that they are not in conflict but rather reflect two different understandings of the question about the ceasing of an instant. 

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