Even though perception was not a central topic to most medieval thinkers, questions about the way we get acquainted with things in the world and their accidental properties such as colors and smells did receive some attention and gave rise to relatively robust systematic reflections. In some cases that was necessitated by the texts medieval authors were commenting, for instance Aristotle’s treatise On the soul, the second book of which deals with the soul of animals and its proper operations of sensation and motion. Animals must perceive objects in their surroundings – see a predator, smell food – in order to pursue or to avoid them. In addition, a certain species of animal, the human species, builds on the information acquired from the senses to come to know something more essential about those perceived objects, namely what makes them to be what they are and what essential properties constitute them. This allows humans to identify and recognize natural kinds and to understand – and thus predict – their behavior. Of course, even before Aristotle’s works dealing with such questions, such as the above-mentioned De anima or the De sensu et sensato, arrived and became known in the Latin West, medieval thinkers were already aware of the need to explain, at least in rough outline, how animals, rational and non-rational, navigated their environment. But until then, the explanations had an overly theological undertone, focusing in most case on human exceptionalism in the natural world as the image of the Creator and on the impact of sin on human cognitive and behavioral capacities and processes.

The Latin translations of Aristotle provided the conceptual tools and in some cases the questions themselves that required more comprehensive, systematic, and naturalistic theories. Whilst expanding on the kind of questions asked about perception, the Aristotelian framework also determined the way the questions were answered, for instance emphasizing a certain direction of fit for cognitive processes: from the operations of the external senses to intellectual abstraction via the functioning of the internal senses. His Arabic commentators, such as Avicenna and Averroes, built on this explanatory framework and provided the template for late medieval theories of perception and cognition. As the result of the comprehensiveness of this theoretical Aristotelian framework, earlier Platonic and neo-Platonic accounts of cognition that emphasized the active nature of perception and the existence of top-down (rational) influences on sensory processes got watered down or even disappeared altogether. And yet, elements of these earlier theories are still there to be found in late medieval authors, if one looks closely. The articles in this volume provide evidence of this fact by focusing on the role of reason and rationality in perception and therefore contribute to a needed reassessment of the complexity of theories of cognition as developed by late medieval thinkers.

This volume is the last major output of the project Rationality in Perception: Transformations of Mind and Cognition 1250–1550 which I directed from April 2015 to March 2020 at the Department of Philosophy, History and Art Studies of the Faculty of Arts of the University of Helsinki, and which would not have been possible without the generous funding from the European Research Council under the grant agreement n. 637747. Many thanks to all the researchers involved in this project, in particular Tuomas Vaura, who was providential in helping to organize the last conference of the project that provided an opportunity for some of the contributors to the volume to meet in person. I am particularly grateful to the authors for their willingness to contribute to the volume, for meeting the strict deadlines, and for their patience in waiting for the editorial process to go through its paces. Many thanks to John Marenbon for accepting this volume in his Investigating Medieval Philosophy series and to the editorial board and an anonymous referee for many helpful comments and suggestions. My final words go to Serena Masolini who generously assisted me with the editorial work in the last stages of preparation of the volume: Many, many thanks!