Doubt

“Doubt is not a pleasant mental state but certainty is a ridiculous one.” 

Voltaire

Don't Doubt Yourself

When you start to doubt yourself, the real world will eat you alive.

~ Henry Rollins

Doubt everything

Doubt everything. Find your own light.

Buddha

A Real Seeker

If you would be a real seeker after truth, it is necessary that at least once in your life you doubt as far as possible, all things.

Rene Descartes