C.S. Lewis & Terry Pratchett

Vimes talking to Carrot about the light:

"Vetinary sits up half the night writing, and in the morning the candle's burned down.  Poisoned by the light.  The light's something you don't see. Who looks at the light? [...]  We don't look at the light because the light is what we look with."  (Pratchett, Feet of Clay 289)

Opening passage of CSL's "Meditation in a Toolshed":

I was standing today in the dark toolshed. The sun was shining outside and through the crack at the top of the door there came a sunbeam. From where I stood that beam of light, with the specks of dust floating in it, was the most striking thing in the place. Everything else was almost pitch-black. I was seeing the beam, not seeing things by it. 

Then I moved, so that the beam fell on my eyes. Instantly the whole previous picture vanished. I saw no toolshed, and (above all) no beam. Instead I saw, framed in the irregular cranny at the top of the door, green leaves moving on the branches of a tree outside and beyond that, 90 odd million miles away, the sun. Looking along the beam, and looking at the beam are very different experiences.