CHAPTER XII

GENERAL CONCLUSIONS

ON SENSATION

             IT must be taken as a general rule that all sensation is the receiving of forms without matter, as wax receives a seal without the iron or gold of the signet-ring. It receives an imprint of the gold or bronze, but not as gold or bronze. Similarly the sense of any sense-object is acted upon by a thing having colour or flavour or sound; not, however, in respect of what each is called as a particular thing, but in so far as each has a certain quality and according to its informing principle.§§ 551-4

             The primary sensitive part is that in which a power of this sort resides. They [part and power] are indeed the same thing, but differ in mode of being. What receives sensation will be an extended magnitude, but neither being sensitive nor sensation is a magnitude. Each is, rather, a certain ratio and power of a magnitude.§ 555

             It is clear from these facts why the excess of sensible qualities destroys the sense-organs. For if the change is too violent for the sense-organ, the ratio [of the latter] is lost,--which [ratio] is the sense. It is as with tone and harmony when the strings are violently struck. Also it is plain why plants have no sensation, though they have some share in soul, and are affected by tangible objects to become hot or cold. The reason is that they lack a mean or principle of this kind, able to receive the forms of sense-objects; they are acted upon materially.§§ 556-7

             It might be asked, is anything affected by odour if it cannot have the sense of smell?--or by colour, if it is unable to see? And so in the other cases.§ 558

             But if what can be smelt is odour, whatever causes smell is odour. Hence things incapable of smelling cannot be affected by odour. The same argument holds for the other senses. And of subjects that can perceive, the ability belongs to them only in virtue of each being sensitive.§ 559

             The same is evident thus: neither light or darkness or sound or odour affect bodies; but only what they occur in does so; e.g. it is the air which accompanies thunder that smashes trees.§ 560

             But things tangible and savours do so affect things. If not, what is it that inanimate things are affected and changed by? § 561

             Therefore, do not also the other sense-objects have a like effect? But not every body is affected by odour or sound,--such recipients being only things indefinite and unstable like air: which may smell as though affected somehow.§ 562

             What then is to smell, save to be 'affected somehow'? But to smell is to sense. Air, however, being so affected, becomes rapidly sensible.§ 563