Graduiertenschule für die Geisteswissenschaften

Dunz, Joschka

"Psychology and Epistemology in Ibn al-Haytham’s Optics.
From Arabic into Latin."

Kontaktadresse an der Universität Würzburg:
Institut für Philosophie
Ehrenhof, Südflügel
97070 Würzburg

E-Mail an Herrn Dunz

Erstbetreuer/in: Prof. Dr. Dag Nikolaus Hasse


Prof. Dr. Jörn Müller

Prof. Dr. Andreas Lammer (Univ. Nijmwegen)

Klasse in der Graduiertenschule:  "Mittelalter und Frühe Neuzeit"

Promotion in der Graduiertenschule ab WS 2022/2023.

In his Optics (Kitāb al-Manāẓir), Ibn al-Haytham (Alhacen) develops the most important theory of vision of the Middle Ages. He understands this theory as a synthesis of the Aristotelian intromission theory and the mathematical theories of Euclid and Ptolemy, who assumed that a cone of rays or flux emerges from the eye to the objects. Ibn al-Haytham uses this cone in his own intromission theory to show how light enters the eye and to prove the assumption of rays to be superfluous.

In the second book of his Optics, Ibn al-Haytham describes a detailed psychological theory, which has received little attention in research. As I argue, however, it is indispensable to his theory of vision. For Ibn al-Haytham states that vision would not be possible by pure sensation alone. Rather, the forms that enter the eye must be processed in the soul by means of judgement, inference, and recognition. These actions happen unnoticed and extremely quickly, due to the soul’s ability to use non-verbal syllogisms. If successful, this process leads to a form existing in the soul which contains all twenty-two visible properties of the visible object.

It is well known that Ibn al-Haytham had great influence on the scientific discussion in the Latin West, especially on the optical theories of Roger Bacon, John Peckham, and Vitello. Nonetheless, the influence of the psychological part of Ibn al-Haytham’s Optics remains still to be investigated. In my dissertation, I analyse Ibn al-Haythams psychological theory and its epistemological implications, as well as its influence on philosophical discussions in the Latin West.