The atmosphere, then, is a medium. A medium permits more or lessunhindered movements of animals and displacements of objects. Funda-mentally, I suggest, this is what is meant by "space." But a medium hasother equally important properties. It also permits the flou; of informa-tion. It permits the flux of light, it transmits vibration, and it mediatesthe diffusion of volatile substances. Only by illumination do animals"see" things, only by vibration do they "hear" things, and only by diffu-sion do they "smell" things. I shall argue that in these three ways variousproperties of a thing are broadcast, as it were, when it is illuminated, orvibrating, or chemically volatile.
Gives definition of "medium": - allows animals move - allows objects get displaced - allows the "flow of information"