Shadow is the absence of light, merely the obstruction of the
luminous rays by an opaque body. Shadow is of the nature of
darkness. Light [on an object] is of the nature of a luminous body;
one conceals and the other reveals. They are always associated and
inseparable from all objects. But shadow is a more powerful agent
than light, for it can impede and entirely deprive bodies of their
light, while light can never entirely expel shadow from a body, that
is from an opaque body.
120.
Shadow is the diminution of light by the intervention of an opaque
body. Shadow is the counterpart of the luminous rays which are cut
off by an opaque body.
This is proved because the shadow cast is the same in shape and size
as the luminous rays were which are transformed into a shadow.
121.
Shadow is the diminution alike of light and of darkness, and stands
between darkness and light.
A shadow may be infinitely dark, and also of infinite degrees of
absence of darkness.
The beginnings and ends of shadow lie between the light and darkness
and may be infinitely diminished and infinitely increased. Shadow is
the means by which bodies display their form.
The forms of bodies could not be understood in detail but for
shadow.
122.