"Seeing that the nature of all things falls into one of two categories (sensible and intelligible, as I was saying), the schools of Aristotle and Theophrastus and the Peripatetics generally acknowledged two criteria for truth: sense for the sensible, and intellect for the intelligible. According to Theophrastus, what is 'manifest' can belong to either category. As a criterion, perception obeys no logic and is not subject to proof, and though it appears prior to intellect in temporal order, intellect has priority over it in terms of its capacity. The sense is stirred by what is sensible, and in the soul of higher animals (such as are capable of movement of their own) another movement is produced from it, in proportion to its clarity with respect to sense. This movement they identify with memory and imagination. Memory is of an affection to the sense, and imagination is of the sensible object which caused the sense to be affected. And so they speak of this kind of movement by analogy to a footprint. Just as the footprint is produced by and from some thing -- by the pressure of a foot, but from some person, let's say Dion -- so too is the above-mentioned movement of the soul produced by some such affection of the sense, and from something quite like the object of sense, to which it retains a certain similarity.
"Furthermore, this movement which can be called memory and imagination includes a third movement after these. This is 'rational imagination,' which is left up to our judgment and follows our choice. This very movement is spoken of as thought, and it is spoken of as mind -- as when for example someone, on encountering Dion, is affected by a sensation and turns away, and by the affection of his sense some image is engendered in his mind (which we earlier called memory, and said it was like a footprint), and from this same image he willfully draws up and fashions a phantásma, such as the category "man." The Peripatetic school of philosophers observe a distinction in this movement of the soul, dividing it into thought and intellect: thought when it is potential, and intellect when it is actualized. For when the soul is capable of fashioning (i.e. is of a nature to do so), it is called thought; and when it is actually engaged in doing so it is called intellect.
"Now from the intellect and thinking arise comprehension, knowledge and art. For thinking is sometimes about individual forms, and sometimes it is about individuals and classes together. The act of making connections between phantásmata of the intellect and gathering individual cases under universal headings is called comprehension, and the final result of all this gathering and classifying are knowledge and art -- knowledge being precise and inerrant, art not so much."
Sextus Empiricus, Against Logicians I.217-24
"Furthermore, this movement which can be called memory and imagination includes a third movement after these. This is 'rational imagination,' which is left up to our judgment and follows our choice. This very movement is spoken of as thought, and it is spoken of as mind -- as when for example someone, on encountering Dion, is affected by a sensation and turns away, and by the affection of his sense some image is engendered in his mind (which we earlier called memory, and said it was like a footprint), and from this same image he willfully draws up and fashions a phantásma, such as the category "man." The Peripatetic school of philosophers observe a distinction in this movement of the soul, dividing it into thought and intellect: thought when it is potential, and intellect when it is actualized. For when the soul is capable of fashioning (i.e. is of a nature to do so), it is called thought; and when it is actually engaged in doing so it is called intellect.
"Now from the intellect and thinking arise comprehension, knowledge and art. For thinking is sometimes about individual forms, and sometimes it is about individuals and classes together. The act of making connections between phantásmata of the intellect and gathering individual cases under universal headings is called comprehension, and the final result of all this gathering and classifying are knowledge and art -- knowledge being precise and inerrant, art not so much."
Sextus Empiricus, Against Logicians I.217-24
