John Blund (ca. 1175-1248) was a Master of Theology at the University of Oxford and, from 1234, Chancellor of York Cathedral. The work of Aristotle "De anima," which is central to philosophy, particularly to the epistemology and scientific theory of the Middle Ages, is systematically interpreted by John Blund with reference to Avicenna. The text translated here is thus an early document of the reception and interpretation of Aristotle's theory of knowledge, but above all, it also reflects the growing interest in natural philosophical questions at the (English) universities of the Latin-speaking Middle Ages.