Although the older branches of physics, particularly optics and acoustics, started from the study of sensory qualities, they are now no longer directly concerned with the perceptible properties of the events with which they are dealing. Nothing is more characteristic of this than the fact that we find it now necessary to speak of ‘visible light’ and ‘audible sound’ when we want to refer to the objects of sense perception.

F. A. Hayek writing about direct and indirect human perception in the book The Sensory Order