“The light of the sun seems to be poured down, and to be poured, indeed, in every direction, but not poured away; for this pouring is an extension, and that is why the sun’s beams are called ‘rays’ (aktines), because they are extended (ekteinesthai).
“And what kind of thing a ray is you can readily see if you look at sunlight entering a darkened room through a narrow opening. For it stretches out in a straight line and comes to rest, so to speak, on any solid body that intercepts it, cutting off the air that lies beyond; and there it rests, neither slipping off nor falling down.
“The pouring forth and diffusion of our understanding should follow a comparable pattern, and by no means be a pouring away, but rather, an extension; and it should not make a forcible or violent impact on the obstacles that it encounters nor sink down, but stand firm and illuminate the object that receives it, for that which fails to welcome it will deprive itself of light.”
– Marcus Aurelius