A doubtful friend is worse than a certain enemy. Let a man be one thing or the other, and we then know how to meet him.

Doubt everything. Find your own light.

Doubt is a pain too lonely to know that faith is his twin brother.

Doubt is the origin of wisdom

Doubt must be no more than vigilance, otherwise it can become dangerous.

Faith without doubt is addiction

I no doubt deserved my enemies, but I don't believe I deserved my friends.

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.

In order to seek truth, it is necessary once in the course of our life to doubt, as far as possible, of all things.

It is better to remain silent and be thought a fool than to open one's mouth and remove all doubt.

It is beyond a doubt that all our knowledge begins with experience.

No doubt exists that all women are crazy; it's only a question of degree.

Science is the outcome of being prepared to live without certainty and therefore a mark of maturity. It embraces doubt and loose ends.

The only limit to our realization of tomorrow will be our doubts of today.

The right of a nation to kill a tyrant in case of necessity can no more be doubted than to hang a robber, or kill a flea.

The trouble with the world is that the stupid are cocksure and the intelligent are full of doubt.

There is nothing more difficult to carry out, nor more doubtful of success, nor more dangerous to handle, that to institute a new order of things

You have to work hard to get to the top of your game. I think every writer has doubts! I still do all the time.