On Sense And The Sensible   

[granting this, then, the question arises]: is the same also true in

the case of Colour and Light? For certainly it is not true that the

beholder sees, and the object is seen, in virtue of some merely

abstract relationship between them, such as that between equals. For

if it were so, there would be no need [as there is] that either [the

beholder or the thing beheld] should occupy some particular place;

since to the equalization of things their being near to, or far

from, one another makes no difference.

Now this [travelling through successive positions in the medium] may

with good reason take place as regards Sound and Odour, for these,

like [their media] Air and Water, are continuous, but the movement

of both is divided into parts. This too is the ground of the fact that

the object which the person first in order of proximity hears or

smells is the same as that which each subsequent person perceives,

while yet it is not the same.

Some, indeed, raise a question also on these very points; they

declare it impossible that one person should hear, or see, or smell,

the same object as another, urging the impossibility of several

persons in different places hearing or smelling [the same object], for

the one same thing would [thus] be divided from itself. The answer

is that, in perceiving the object which first set up the motion- e.g.

a bell, or frankincense, or fire- all perceive an object numerically

one and the same; while, of course, in the special object perceived

they perceive an object numerically different for each, though

specifically the same for all; and this, accordingly, explains how it

is that many persons together see, or smell, or hear [the same

object]. These things [the odour or sound proper] are not bodies, but

an affection or process of some kind (otherwise this [viz.

simultaneous perception of the one object by many] would not have

been, as it is, a fact of experience) though, on the other hand, they

each imply a body [as their cause].

But [though sound and odour may travel,] with regard to Light the