There is nothing we need to do that isn't dangerous.

It is dangerous to attach probability zero to anything other than a logical impossibility.

The threat lies in the realization that in our universe the security of stable, permanent rules are gone forever. We are living in a dangerous and uncertain world that inspires no blind confidence. Our hope arises from the knowledge that even small fluctuations may grow and change the overall structure. As a result, individual activity is not doomed to insignificance

After all, dangers are everywhere; those who turn back because of dangers will never succeed in any life that we can imagine.

My point is not that everything is bad, but that everything is danger­ous, which is not exactly the same as bad. If everything is dangerous, then we always have something to do. So my position leads not to apa­thy but to a hyper- and pessimistic activism. I think that the ethico-political choice we have to make every day is to determine which is the main danger.

What thing so good which not some harm may bring?
Even to be happy is a dangerous thing.

Our generation faces only one danger, that we might say to ourselves this is not our problem, and that we will pass it off to the distant future. That we might shrug and say to ourselves that a thousand years is a long time. That we will become complacent and conclude that this problem will take care of itself.
But I say to you, we should take no satisfaction in the fact that we ourselves are in no physical danger. This is a hazard to our world, to everything we hope to pass on to future generations. And it is clear that we should act now, while we have the time.

There is far more danger of harm than there is hope of good in any radical changes.

Hope could be dangerous, desire could be catastrophic.

But have heart. Hope is something that can be very dangerous but without it life would be horribly dry. Impossible, even. Take it from me.

Dangers don't hurt us. Only things that happen ever hurt anyone, and a danger is a thing that might happen and might not happen, and sometimes don't amount to shucks.

I consider it an extremely dangerous doctrine, because the more likely we are to assume that the solution comes from the outside, the less likely we are to solve our problems ourselves.

My fellow citizens: let no one doubt that this is a difficult and dangerous effort on which we have set out. No one can see precisely what course it will take or what costs or casualties will be incurred. Many months of sacrifice and self-discipline lie ahead--months in which our patience and our will will be tested--months in which many threats and denunciations will keep us aware of our dangers. But the greatest danger of all would be to do nothing.

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