Aristotle's "De anima" ("On the Soul") divides the mind into three parts: sensation, imagination and intellection. When one perceives an object, his mind composites a sense-image. When he remembers the object he previously sensed, he is imagining its form (the image of the imagination is often translated as "phantasm"). When he extracts information from this phantasm, he is using his intellect. Consequently, all human knowledge concerning universals (such as species and properties) are derived from the phantasm ("the received is in the receiver according to the mode of the receiver"), which itself is a recollection of an experience. Concerning the question of "Whether the intellect can actually understand through the intelligible species of which it is possessed, without turning to the phantasms?" in the "Summa Theologica", Aquinas quotes Aristotle in the "sed contra": "the soul understands nothing without a phantasm." Hence the peripatetic axiom. (Another theorem to be drawn from this is that error is a result of drawing false conclusions based on our sensations.)