In order to determine whether we can know anything with certainty, we first have to doubt everything we know

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

The scientist has a lot of experience with ignorance and doubt and uncertainty, and this experience is of very great importance, I think. When a scientist doesn’t know the answer to a problem, he is ignorant. When he has a hunch as to what the result is, he is uncertain. And when he is pretty damn sure of what the result is going to be, he is still in some doubt. We have found it of paramount importance that in order to progress, we must recognize our ignorance and leave room for doubt. Scientific knowledge is a body of statements of varying degrees of certainty — some most unsure, some nearly sure, but none absolutely certain. Now, we scientists are used to this, and we take it for granted that it is perfectly consistent to be unsure, that it is possible to live and not know. But I don’t know whether everyone realizes this is true. Our freedom to doubt was born out of a struggle against authority in the early days of science. It was a very deep and strong struggle: permit us to question — to doubt — to not be sure. I think that it is important that we do not forget this struggle and thus perhaps lose what we have gained.

Instead of striving for certainty, we should be in constant search of doubt: doubt about our own beliefs, doubt about our own feelings, doubt about what the future may hold for us unless we get out there and create it for ourselves. Instead of looking to be right all the time, we should be looking for how we’re wrong all the time. Because we are.

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.

More often than you might think, teaching science is inseparable from teaching doubt.

But I begin to wonder if doubt is better than the wrong knowledge.

We must surrender our skepticism only in the face of rock-solid evidence. Science demands a tolerance for ambiguity. Where we are ignorant, we withhold belief. Whatever annoyance the uncertainty engenders serves a higher purpose: It drives us to accumulate better data. This attitude is the difference between science and so much else. Science offers little in the way of cheap thrills. The standards of evidence are strict. But when followed they allow us to see far, illuminating even a great darkness.

Pour examiner la vérité, il est besoin, une fois dans sa vie, de mettre toutes choses en doute autant qu’il se peut.

Doubt everything. Find your own light.

Actually, I do have doubts, all the time. Any thinking person does. There are so many sides to every question.

if you don't have doubts you're either kidding yourself or asleep. Doubts are the ants-in-the-pants of faith. They keep it alive and moving.

Philosophy begins when one learns to doubt — particularly to doubt one’s cherished beliefs, one’s dogmas and one’s axioms.

Our freedom to doubt was born out of a struggle against authority in the early days of science. It was a very deep and strong struggle: permit us to question — to doubt — to not be sure. I think that it is important that we do not forget this struggle and thus perhaps lose what we have gained.