“Minima sensibilia”. The Medieval Latin Debate (ca. 1250-ca. 1350) and Its Roots

The thesis focuses on one of the least studied topics in Medieval Latin Aristotelian natural philosophy (ca. 1250-ca. 1350), i.e., the so-called topic of “minima sensibilia”. If, as claimed most notably in “Physics” VI, magnitudes are (potentially) infinitely divisible, a dilemma arises with respect to the limits of the divisibility of sensible qualities through the division of the matter (considered as an extended magnitude) with which they are united. Either sensible qualities are also (potentially) infinitely divisible (but this implies that the senses should have an infinite power in order to perceive them, against a fundamental Aristotelian assumption concerning the limits of every power existing in nature), or they are not (potentially) infinitely divisible (in this case, however, there would be portions of matter that can neither be cognised by the senses nor, evidently, by the intellect, and, what is worse, sensible entities would be ultimately composed of them, something entirely unacceptable in the Aristotelian worldview). To solve the dilemma, Aristotle, in Chapter 6 of the “De sensu et sensato” (445b3-446a20), makes use of the distinction between act and potency, affirming that sensible qualities are infinitely divisible in potency as part of the whole to which they belong, but there are minimal quantities of matter that can exist in act on their own endowed with their sensible qualities. The thesis investigates the reflection conducted by Medieval Latin commentators of the “De sensu et sensato” (always read in connection with their Greek and Islamic sources) on the subject of “minima sensibilia”, using it as a privileged gateway to study from a new and original point of view the Medieval Latin conception of the ontology and of the epistemology of sensible qualities. Indeed, through a close scrutiny of the debate (which is accompanied by a thorough reconstruction of the complex manuscript tradition of Medieval Latin “De sensu” commentaries, that have hitherto been largely neglected by scholars) it is demonstrated that Medieval Latin commentators progressively developed a conception according to which sensible qualities can exist on their own in the natural world without being perceptible in act due to the smallness of the matter with which they are united. Such sensible qualities (that are sometimes called “insensibilia propter parvitatem”) can, nevertheless, become perceptible in act by uniting with each other. Thanks to this fundamental development, not only sensible qualities started to be understood mostly in autonomy from their role in perception, but the sensible world became suddenly much more extended than the world that can be perceived by the senses, with the consequence that the confidence in the human ability to cognise its ultimate structure began to crumble.