The Opus Majus of Roger Bacon

is the contrary, and this is especially in earth, and secondarily in fire. Here, however, moisture is called by the term for liquid and lubricous, and dry is called arid and coagulated. And it is so with many others that are reduced to the species and principal modes of visible things enumerated above. And all these are evident from the first book of Ptolemy’s Opticis Optics and from the second book of Alhazen’s De Aspectibus On Aspects, and from other authors of perspective. And they are common sensibles, concerning some of which Aristotle gives examples in the second book De Anima and in the beginning of De Sensu et Sensato, such as magnitude, figure, motion, rest, and number; but these are not the only common sensibles, but all those previously mentioned, although the common herd of natural philosophers does not consider this, because it is not experienced through the science of perspective. For common sensibles are not so called because they are sensed by the common sense, but because they are commonly determined by all particular senses or by many, and especially by sight and touch, because Ptolemy says in the second book of his Perspectiva Perspective that touch and sight communicate in all these twenty note: Bacon is referring to his list of common sensibles here.. And these twenty-nine, along with those that are reduced to them, are sensed by the particular senses, and by the common sense, and by the imagination, and these virtues of the soul cannot judge concerning other sensibles by themselves except accidentally.

CHAPTER IV.

Concerning the investigation of the estimative, memorial, and cogitative faculty.

The faculty of judgement.

There are, however, other sensibles [perceived] by themselves. For brute animals use only sense, because they do not have intellect. And a sheep, if it has never seen a wolf, flees from it immediately, and every animal fears at the roar of a lion, even if it has never heard or seen it before, and so it is with many things that are harmful and contrary to the constitution of animals. And in the same way with things that are useful and convenient. For if a lamb has never seen a lamb, it runs to it and willingly stays with it, and so it is with others. Brute animals, therefore, sense something in convenient and harmful things...