Good question.

Descartes was a philosopher in the 1600's I who set out to solve this as he wanted to live only in reality. A noble venture.

He spent his life trying to find 4 pillars of Universal truth.

He only found one. "I am a thinking thing". Or "I think, therefore I am."

An extremley intellegent man. I agree with him. From here it gets sticky. I beleive their are many realities. It's a state of mind.

One should work hard to not allow people who will blatently lie to you in an effort to control you for their own purposes at all costs though.

The individual is so precious.