Candle Light from "Zen: The perfect Companion"

A quote from Zen : The Perfect Companion, which I like to read because it has koans, stories, and commentary that follow. The following is from the book.

Candle light

One evening, Zen Master Man Gong lit a candle by the window in his room. He then asked his attendant, "Which is the true light, the candlelight or the light reflected in the window?"
The attendant blew out the candle and said, "Master, what can you do?" Man Gong then re-lit the candle.

Commentary:
No eyes, no light. No mouth, no speech. If you turn on the light, the room is bright. If you turn off the light, the room is dark.