IAS Lecture: Can We Count the Uncountable?
Guest Lecturer: Professor Paolo Mancosu, USA
How Many Points are in a Line Segment? From Grosseteste to Numerosities
The Institute of Advanced Studies invites you to the lecture by Professor Paolo Mancosu from the Department of Philosophy of the University of California.
Professor Massa is visiting Tel Aviv University as part of the Lowy Distinguished Guest Professors series 2025–2026 and will speak at the Logic in Philosophy Distinguished Lecture Series in Memory of Ruth Manor.
In his commentary on Aristotle’s Physics, the medieval scholar Robert Grosseteste proposed that the numerosity of points in a finite line segment varies proportionally with its length. His view sparked significant debate in the 13th century, particularly after Richard Fishacre introduced a one-to-one correspondence between points on line segments of different lengths.
In his lecture, Professor Mancosu will reconstruct key aspects of this medieval discussion, connect it to later developments in the thought of Bolzano and Cantor, and present recent results from the modern theory of numerosities. These results show that counting points in a line segment, while preserving the part–whole principle, can be made compatible with Lebesgue measure, offering a surprising mathematical framework in which Grosseteste’s intuitions find coherent expression
When: December 10, 2025 | 16:00
Where: Gilman Building, Room 449
Light refreshments will be served before the lecture.
The lecture will be conducted in English and is open to the public.
View the invitation flyer
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