The more of this there is, the less you see. What is it?

How to think about it

1. Most things become more visible when there is more of them, so the answer must be an absence of something you need to see.
2. Fog and smoke reduce visibility, but they are things that block light rather than the lack of light itself.
3. The hint points to turning off the lights. What fills a room when the light goes out?
4. Darkness: the more of it there is, the less you can see.

Why “Darkness” is the answer

Darkness is the absence of light, and seeing requires light, so more darkness means less sight. The riddle works because we talk about darkness as if it were a substance that can increase, even though it is really a lack. Fog is a close alternative, but fog is a thing, while darkness is the shortage of the thing you need.

Common wrong answers

• Fog. Thick fog does hide things, so it is a reasonable guess; the lights-off hint points to darkness.
• Sunlight. Too much sunlight makes you squint, but in general more light lets you see more.