Mescaline

Mescaline is a hallucinogen. If you consume it, you hallucinate. When you hallucinate, you see things that don't really exist. Paralells have sometimes been drawn between seeing things that don't exist and being crazy.

If one is intelligent enough, one can take mescaline and have a wholly entertaining experience that does not make one turn into a bible thumping idiot. If one is too foolish, one is doomed to be reduced to idiot status, if one is not already there.