Dr. Yael Kedar – Freiburg Institute for Advanced Studies

Dr. Yael Kedar

Tel Hai College
Philosophy

Senior Fellow
FRIAS Fellowship Programmes

September 2025 – February 2026

Last Update: 01.10.2025

Curriculum Vitae

Yael Kedar is a senior lecturer in philosophy at Tel Hai College. She specializes in late medieval philosophy, with a focus on epistemology, scientific method, and philosophy of nature. She has written on light and color – their ontological status and their perception; on physical causality, the concept of laws of nature, the quantification of physics, and on the Medieval scientific method. She serves as the vice president of the Roger Bacon Research Society and the Middle East convenor of the International Robert Grosseteste Society. She edited several special peer-reviewed journal issues on the following topics: laws of nature, quantities, Roger Bacon, and is now engaged in editing a special issue on the medieval concept of infinity. She is a co-chief editor of the Routledge book series Global Perspectives on Natural Philosophy. She won several ISF (Israel Science Foundation) grants and organized two large-scale ISF workshops. She was a research fellow at Georgetown University, Friedrich Alexander University in Erlangen, and at the Thomas Institute at the University of Koln. Her publications include papers in top-notch journals such as Synthese, Journal for the History of Philosophy, and Studies in the History and Philosophy of Science, as well as book chapters and encyclopedia entries. Her current projects deal with Medieval Franciscan science in general and with the thirteenth-century concepts of space and heaviness in particular.

Selected Publications

2017 with Hon G, “‘Natures’ and ‘Laws’: The Making of the Concept of Law of Nature Robert Grosseteste (c. 1168 – 1253) and Roger Bacon (1214/1220 – 1292)”. Studies in the History and Philosophy of Science Part A 61: 21-31.
2020 with Demange D, “Physical action, species, and matter: The debate between Roger Bacon and Peter John Olivi”. Journal for the History of Philosophy 58: 49–59.
2024 “Colours and their Species – Apparent or Real? Roger Bacon’s Mature Colour Theory”. In Decaix, V. and Ierodiakonu, K (eds.), Theories of Colour from Democritus to Descartes. London: Routledge, pp. 199-215.
2024 “Propter Quid Demonstrations: Roger Bacon on Geometrical Causes in Natural Philosophy”, Synthese 203(1): 1-24.
2025 “The Geometrical Atomism of Roger Bacon”. British Journal for the History of Philosophy 33(2): 285-302.

FRIAS Project

Principles of the Distribution of Matter in the Cosmos of Thirteenth-Century Franciscan Thought

One of the fundamental breakthroughs of the scientific revolution of the seventeenth century was the development of a systematic and quantified understanding of mass which was introduced as a novel concept. So, what was there before the introduction of this novel concept? I plan to reconstruct the medieval concepts of heaviness, density, and gravity as organizing principles of the arrangement of elemental matter and the motions of bodies to their natural place. Although the concept of weight, independent of motion, and the concept of mass were absent, some medieval commentators realized that another type of quantity of matter is required to account for natural processes, other than volume. Indeed, one can find medieval possible precursors of these concepts in the fourteenth century, such as Giles of Rome and Duns Scotus. The project seeks to identify precursors and sources of the concepts of weight and mass among the Franciscans of the thirteenth century, before Giles and Scotus. These include Robert Grosseteste, Roger Bacon, Richard of Middleton, and Geoffrey of Aspall. The project will facilitate comprehension of the gradual making of concepts of attraction, gravity, weight and mass. This would make a fundamental contribution to understanding the development of science from antiquity to modernity.