OF THE NATURE OF SHADOW.

Shadow partakes of the nature of universal matter. All such matters
are more powerful in their beginning and grow weaker towards the
end, I say at the beginning, whatever their form or condition may be
and whether visible or invisible. And it is not from small
beginnings that they grow to a great size in time; as it might be a
great oak which has a feeble beginning from a small acorn. Yet I may
say that the oak is most powerful at its beginning, that is where it
springs from the earth, which is where it is largest (To return:)
Darkness, then, is the strongest degree of shadow and light is its
least. Therefore, O Painter, make your shadow darkest close to the
object that casts it, and make the end of it fading into light,
seeming to have no end.

Of the various kinds of shadows. (123-125).