Give me some tough riddles, and I'll give you ten points.?

[The Mad Hatter]

The one with the best, most tough riddles win. It's alright if it's a trick question.
Also, it can be something like, "What determines if the glass is half empty or half full?", or "If everything is as it shouldn't, then should what shouldn't be what is?". I love confusing people like that. Include answers, if you will.

Also, if you can answer my riddle logically, you'll have a better chance of getting picked.
What turns everything around, but itself cannot move?

 

[Ruby]

Perspective?

What walks on 4 legs in the morning, 2 legs in the afternoon, and 3 legs in the evening?

This is the famous riddle in the story of the sphinx.