Mathematical Mirror

under figure and arrangement. And like rectitude, curvature, concavity, and convexity, which are placed under figure; and multitude and paucity under number; and like equation, increase, and diminution, which are placed under consimilarity and diversity; and like cheerfulness, laughter, and sadness, which are comprehended from the figure of the form of the face; and weeping, which is comprehended from the figure of the face along with the movement of tears; and like humidity and dryness, which are placed under motion and rest. For humidity is not comprehended by the sense of vision except from the liquidity of a moist body and from the motion of one part of it before another, and dryness is comprehended from the retention of the parts of the dry thing and from the privation of liquidity. Here, however, it must be considered that Aristotle, in Book 2 of On Generation, maintains that the moist and the dry are in one way the primary qualities, which are owed most of all to the elements, and through them, humidity and dryness arise in elemental things, which are reduced to the primary ones and are caused by them. Therefore, it has been said concerning the primary ones that they are proper sensible things, perceivable by touch alone. Mention is made here of the others. For the primary humidity is that which easily passes into all figures, being difficult to terminate of itself but well-terminated by an alien boundary, as is the case in air most of all, and then in water. Dryness is the contrary, and this is most of all in earth, and secondarily in fire. Here, however, "moist" is used for the liquid and the slippery, and "dry" is used for the arid and the coagulated. And it is so for many others, which are reduced to the species and principal modes of visible things enumerated above. And all these things are evident from Ptolemy’s first book On Optics, from Alhazen’s second book On Aspects, and from other cultivators of perspective. And they are common sensible things, of which Aristotle gives examples in Book 2 On the Soul and in the beginning of On Sense and the Sensible, such as magnitude, figure, motion, rest, and number. But these are not the only common sensible things, but all those aforementioned are as well, although the common herd of natural philosophers does not consider this, because it is not experienced in the science of perspective. For common sensible things