Opus Majus of Roger Bacon, Vol. II (Burke English trans.)

are the proper objects of sense and perceptible by touch alone. We are speaking, however, concerning the others. For primary moistness is that which passes over easily into all forms, possessing no definite bounds of its own, but conforming readily to the limits of something else, as in the case of air particularly and next in order in the case of water. Dry is the opposite, particularly in the case of earth, secondarily in the case of fire. But here moistness is used in the sense of liquid and slippery, and dry in the sense of arid and coagulated. The same is true concerning many other attributes, which are reduced to the forms and principal modes enumerated above belonging to visible things. All these matters are explained in the first book of Ptolemy on Optics and in the second book of Alhazen on Aspects, and in other authors on optics. There are, moreover, common qualities, some of which Aristotle defines in the second book On the Soul and in the beginning of his work On Sense and the Sensible, as, for example, magnitude, figure, motion, rest, and number. These are not the only common qualities, but also all those mentioned before, although most writers on the subjects of nature do not consider this fact, because they are not expert in the science of optics. For common properties are not so called because they are perceived by the common sense, but because they are determined by all the special senses or by several of them, and particularly by sight and touch, since Ptolemy states in his second book on Optics that touch and sight participate in all these twenty. These twenty-nine, with those that are reduced to them, are apprehended by the special senses, and by the common sense, and by imagination, and these faculties of the soul cannot judge of themselves concerning other qualities except by accident.

CHAPTER IV

BUT there are other sensibles per se original: "sensibles per se" meaning things perceptible by themselves, for animals use sense alone, since they do not possess intellect. The sheep, even if it has never seen a wolf, flees from it at once; and every animal experiences fear at the roaring of a lion, although it has never