What is perceiving?

My analysis of the sense-organs has followed the same pattern. There are two central claims. (1) The sense-faculty is defined by its ability to be changed by the sense-object as such. This ability belongs to an attribute. For instance, the ability to be changed by sound belongs to resonance. (2) The attribute is present only in a certain sort of matter. This, for example, is why we have an ear whose inside is composed of still air, for it is only still air (or water) that is resonant. The sense-organ is here hypothetically necessary in the same way that iron is necessary if the saw is to have the ability to saw.

The sense-organ is in this way explained as a necessary material basis for the first actuality that defines the sense-faculty. The analysis shows that a material basis is necessary if the first actuality to be changed by a certain sort of sense-object is to be present. So far then the focus has been on the relationship between the first actuality and the matter or potentiality of the sense-organ. The analysis has not shown that a material basis is necessary because the first actuality can only be actualised in a material change. Suggestions have been made at various points to the effect that there need be no material changes in perception.