There is nothing more dreadful than the habit of doubt. Doubt separates people. It is a poison that disintegrates friendships and breaks up pleasant relations. It is a thorn that irritates and hurts; it is a sword that kills.
The moment you doubt whether you can fly, you cease for ever to be able to do it.
The worst enemy to creativity is self-doubt.
Doubt isn’t the opposite of faith; it is an element of faith.
The first principle is that you must not fool yourself and you are the easiest person to fool.
Religion is a culture of faith; science is a culture of doubt.
I was feeling insecure you might not love me anymore.
I’m not okay.
If there is anyone out there who still doubts that America is a place where all things are possible; who still wonders if the dream of our founders is alive in our time; who still questions the power of our Democracy; Tonight is your answer.
In all affairs it’s a healthy thing now and then to hang a question mark on the things you have long taken for granted.
I would never die for my beliefs because I might be wrong.
The deepest sin against the human mind is to believe things without evidence.
Fear and self-doubt have always been the greatest enemies of human potential.
All fanaticism is repressed doubt.
We want to have certainties and no doubts – results and no experiments – without even seeing that certainties can arise only through doubt and results only through experiment.