phenomena brought about by light.

There is first the general assumption that light as such is visible. In
order to realize that light is itself an invisible agent, we need only
consider a few self-evident facts - for instance, that for visibility
to arise light must always encounter some material resistance in space.
This is, in fact, an encounter between light, typifying levity, and the
density of the material world, typifying gravity. Accordingly, wherever
visible colours appear we have always to do with light meeting its
opposite.

Optics, therefore, as a science of the physically perceptible is never
concerned with light alone, but always with light and its opposite
together. This is actually referred to in Ruskin's statement, quoted in
the last chapter, where he speaks of the need of the 'force' and of the
intercepting bodily organ before a science of optics can come into
existence. Ruskin's 'light', however, is what we have learnt with
Goethe to call 'colour', whereas that for which we reserve the term
'light' is called by him simply 'force'.

All this shows how illusory it is to speak of 'white' light as
synonymous with simple light, in distinction to 'coloured' light. And
yet this has been customary with scientists from the time of Newton
until today, not excluding Newton's critic, Eddington. In fact, white
exists visibly for the eye as part of the manifested world, and is
therefore properly characterized as a colour. This is, therefore, how
Goethe spoke of it. We shall see presently the special position of
white (and likewise of black), as a colour among colours. What matters
first of all is to realize that white must be strictly differentiated
from light as such, for the function of light is to make visible the