If we have an atom that is in an excited state and so is going to emit a photon, we cannot say when it will emit the photon. It has a certain amplitude to emit the photon at any time, and we can predict only a probability for emission; we cannot predict the future exactly.

You know, people talk about this being an uncertain time. You know, all time is uncertain. I mean, it was uncertain back in – in 2007, we just didn’t know it was uncertain. It was – uncertain on September 10th, 2001. It was uncertain on October 18th, 1987, you just didn’t know it.

Why should I be studying for a future that soon may not exist?

We know what we are, but know not what we may be.

What is this world that is hastening me toward I know not what, viewing me with contempt?

If you aren’t in the moment, you are either looking forward to uncertainty, or back to pain and regret.

I don’t know what can be so dangerous about giving people hope.

Although our intellect always longs for clarity and certainty, our nature often finds uncertainty fascinating.

When I was a little girl, I always dreamed of being a star. I didn’t really know what all that meant. I didn’t know.

There’s no point in making predictions. It’s not worth speculating because nothing is set in stone and things change all the time in football. Today there are opportunities that no one knows if they will come round again in the future.

My comedy is different every time I do it. I don’t know what the hell I’m doing.

I cannot discover that anyone knows enough to say definitely what is and what is not possible.

I accept chaos, I’m not sure whether it accepts me.

It’s a very confusing era that we’re in.

Life’s short. Anything could happen, and it usually does, so there is no point in sitting around thinking about all the ifs, ands and buts.

If you only do things where you know the answer in advance, your company goes away.

Obviously I faced the possibility of not returning when first I considered going. Once faced and settled there really wasn’t any good reason to refer to it.

We cannot wish for that we know not.

I might just write a novel next. I don’t know!

I don’t think you ever really know what all you’re doing, so you have to act on faith.

Often one postulates that a priori, all states are equally probable. This is not true in the world as we see it. This world is not correctly described by the physics which assumes this postulate.

There are too many accidents that can befall life on a single planet.

A hustler has to deal with danger and risk. It’s part of the game. You cannot control it all, nor would you want to. Chaos, unknown factors are not something to be anxious about.

Talent without discipline is like an octopus on roller skates. There’s plenty of movement, but you never know if it’s going to be forward, backwards, or sideways.

I don’t know where I’m going from here, but I promise it won’t be boring.

If we must not act save on a certainty, we ought not to act on religion, for it is not certain. But how many things we do on an uncertainty, sea voyages, battles!

Life is anything but predictable.

Life is a gamble. You can get hurt, but people die in plane crashes, lose their arms and legs in car accidents; people die every day. Same with fighters: some die, some get hurt, some go on. You just don’t let yourself believe it will happen to you.

I want to marry Arline because I love her – which means I want to take care of her. That is all there is to it. I want to take care of her. I am anxious for the responsibilities and uncertainties of taking care of the girl I love.

There are many things that I don’t understand.

Younger people have greatest fears. Why is that? Because they don’t know the plot. They don’t know their own individual plot… they don’t know what’s going to happen to them.

My kind of composing is more like the work of a gardener. The gardener takes his seeds and scatters them, knowing what he is planting but not quite what will grow where and when – and he won’t necessarily be able to reproduce it again afterwards either.

The probability that we may fail in the struggle ought not to deter us from the support of a cause we believe to be just.

Do not keep saying to yourself, if you can possibly avoid it, ‚But how can it be like that?‘ because you will get ‚down the drain,‘ into a blind alley from which nobody has yet escaped. Nobody knows how it can be like that.

We are like boxers, one never knows how much longer one has.

For my part I know nothing with any certainty, but the sight of the stars makes me dream.

Being at ease with not knowing is crucial for answers to come to you.

It is not scientifically possible to accurately predict the outcome of an action. To suggest otherwise runs contrary to historical experience and the nature of war.

As soon as questions of will or decision or reason or choice of action arise, human science is at a loss.

Some people feel affronted when something they thought to be true doesn’t happen. If that’s the case, then your sense of risk is much higher, and that leads to risk aversion. You need to be able to be comfortable in uncertainty.

You never know with these things when you’re trying something new what can happen. This is all experimental.

And no, we don’t know where it will lead. We just know there’s something much bigger than any of us here.

Our lifelong certainties about the world can be demolished in a single second.

The woman that deliberates is lost.

The future is called ‚perhaps‘, which is the only possible thing to call the future. And the important thing is not to allow that to scare you.

When in doubt, don’t.

We fear that this moment will end, that we won’t get what we need, that we will lose what we love, or that we will not be safe. Often, our biggest fear is the knowledge that one day our bodies will cease functioning. So even when we are surrounded by all the conditions for happiness, our joy is not complete.

Risk comes from not knowing what you’re doing.

He that waits upon fortune, is never sure of a dinner.

A wet spot on the floor kind of put a scare in myself, so you never know inside those lines what might happen.

It’s so hard to know what to do when one wishes earnestly to do right.

The uncertainty of parenting can bring up feelings in us that range from frustration to terror.

America is not nearly done. We’re only in the beginning. Who knows who we will be? Who knows… what color we will be? It is all something that, maybe, our descendants – if they survive that long – will see.

If a man will begin with certainties, he shall end in doubts, but if he will content to begin with doubts, he shall end in certainties.

There is no hope unmingled with fear, and no fear unmingled with hope.

It is in the admission of ignorance and the admission of uncertainty that there is a hope for the continuous motion of human beings in some direction that doesn’t get confined, permanently blocked, as it has so many times before in various periods in the history of man.

We always live in an uncertain world. What is certain is that the United States will go forward over time.

We think that life develops spontaneously on Earth, so it must be possible for life to develop on suitable planets elsewhere in the universe. But we don’t know the probability that a planet develops life.

Some scientists believe climate change is the cause of unprecedented melting of the North Pole, and that effects these very uncertain weather patterns. I think we should listen to those scientists and experts.

The more I see the less I know for sure.

I believe the most solemn duty of the American president is to protect the American people. If America shows uncertainty and weakness in this decade, the world will drift toward tragedy. This will not happen on my watch.