Human and animal passions in medieval thought In medieval culture the reference to animal passions was mostly used as a tool for distinguishing the specifically human traits characterized by rationality from all the irrational behaviours or attitudes that make man similar to the animal and which are, therefore, regarded as vices. On the contrary, in the psychology of Thomas Aquinas, passions are indifferent from the moral point of view and they represent a common feature of humans and animals. Both men and animals have a sensitive appetite, which is divided into concupiscible and irascible, from which eleven passions are derived. However on the basis of data provided by Aristotle's zoology, Thomas distinguishes within the animal world different cognitive abilities, which determine important differences even in emotional reactions.