"In this paper I wish to argue that in 13th century epistemology, the perception of the physical world did include the apprehension of complex states of affairs which could also be grasped by some animals. By discussing Avicenna's and Aquinas' points of view regarding the concept of sensibile per accidens and the mental faculties of perception (vis aestimativa and vis cogitativa), I conclude that the perceptual act of discerning complex states of affairs is based upon a background knowledge in which language is a non-essential feature"--Pág. [305].