[Teachings of "calor innatus" in the Latin Canon medicinae of Avicenna].

This contribution examines the natural philosophy behind Avicenna's treatment of the basic physiological concepts of "innate heat", "innate spirit" and "natural moisture" in his famous "Canon medicinae" and in the short tractate "De medicinis cordialibus" usually appended to it in its Latin editions. Contrary to current belief, these concepts, far from being concisely systematized, fulfill a range of differing explicatory functions within the "Canon", which can only with great difficulty be assembled to form a homogeneous, non-contradictory theory. Furthermore, Avicenna differs in essential points from orthodox aristotelian-galenist teaching, particularly regarding the celestial origin of the unrenewable, life-preserving faculties of the "innate heat". It is suggested that the "Canon's" unparalleled popularity may have been due not so much to its systematic form, but to the need of scholarly (re)interpretation, as witnessed by many contemporary commentaries, which offered ample opportunity to academic physicians to show their learning and wit.