Any riddle (preferably ancient) with a profound philosophical, logical, or ethical value?

Question

Please include the answers (I'm asking this for a reason not a challenge). Thank you very much

Answer 1

"The key to life and death is everywhere to be found, but if you do not find it in your own house, you will find it nowhere. Yet, it is before everyone's eyes; no one can live without it; everyone has used it. The poor usually possess more of it than the rich; children play with it in the streets. The meek and uneducated esteem it highly, but the privileged and learned often throw it away. When rejected, it lies dormant in the bowels of the earth. It is the only thing from which the Philosopher's Stone can be prepared, and without it, no noble metal can ever be created."

answer:
http://www.alchemylab.com/riddle.htm

Answer 2

The third age ancient enough for you?

This thing all things devours
Birds, beasts, trees, flowers

Gnaws iron, bites steel,
Grinds hard stones to meal,

Slays king, ruins town,
And beats high mountain down!