A man with a conviction is a hard man to change. Tell him you disagree and he turns away. Show him facts or figures and he questions your sources. Appeal to logic and he fails to see your point.

At about the age of sixteen, I began to feel uneasy. My confidence in adults began to be shaken. They were not smarter than us kids. They just had fixed ideas and stuck to them even if they disagreed among themselves. They were dragging us along a road to an unknown destination; they had no goal, just something to escape from: nature. … It was better to begin to look for a safer, side track. I began to feel like a prisoner calmly preparing to jump off a train that was on a wrong track.

Eugene Dubois is no hero in my book, if only because I share the spirit of his unorthodoxies, but disagree so strongly with his version, and regard his supporting arguments as so weakly construed and so willfully blind to opposing evidence (the dogmatist within is always worse than the enemy without).

First you guess. Don’t laugh, this is the most important step. Then you compute the consequences. Compare the consequences to experience. If it disagrees with experience, the guess is wrong. In that simple statement is the key to science. It doesn’t matter how beautiful your guess is or how smart you are or what your name is. If it disagrees with experience, it’s wrong.

Here’s to the crazy ones. The misfits. The rebels. The troublemakers. The round heads in the square holes. The ones who see things differently. They’re not fond of rules. You can quote them. Disagree with them. Glorify or vilify them. But the only thing you can’t do is ignore them. Because they change things. They push the human race forward. And while some may see them as the crazy ones, we see genius. Because the people who are crazy enough to think they can change the world, are the ones who do.

Humans everywhere share the same goals when the context is large enough. And the study of the Cosmos provides the largest possible context … . If a human disagrees with you, let him live. In a hundred billion galaxies, you will not find another … . If we are to survive, our loyalties must be broadened further, to include the whole human community, the entire planet Earth.

I have always assumed, and I now assume, that he [Robert Oppenheimer] is loyal to the United States. I believe this, and I shall believe it until I see very conclusive proof to the opposite. … [But] I thoroughly disagreed with him in numerous issues and his actions frankly appeared to me confused and complicated. To this extent I feel that I would like to see the vital interests of this country in hands which I understand better, and therefore trust more.

I think all this superstring stuff is crazy and is in the wrong direction. I don’t like that they’re not calculating anything. I don’t like that they don’t check their ideas. I don’t like that for anything that disagrees with an experiment, they cook up an explanation… It doesn’t look right.

If it [a hypothesis] disagrees with experiment, it’s wrong. In that simple statement, is the key to science: it doesn’t make any difference how beautiful your guess is; it doesn’t make any difference how smart you are, who made the guess, or what his name is—if it disagrees with experiment, it’s wrong; that’s all there is to it.

In general, we look for a new law by the following process. First, we guess it. Then we—don’t laugh, that’s really true. Then we compute the consequences of the guess to see if this is right—if this law that we guessed is right—we see what it would imply. And then we compare those computation results to nature—or, we say compare to experiment or experience—compare it directly with observation to see if it works. If it disagrees with experiment, it’s wrong.

Notable enough, however, are the controversies over the series 1 – 1 + 1 – 1 + 1 – … whose sum was given by Leibniz as 1/2, although others disagree. … Understanding of this question is to be sought in the word “sum”; this idea, if thus conceived—namely, the sum of a series is said to be that quantity to which it is brought closer as more terms of the series are taken—has relevance only for convergent series, and we should in general give up the idea of sum for divergent series.

Some books are like grindstones, good to sharpen your wits on just because you disagree from them.

The worst primary school scolding I ever received was for ridiculing a classmate who asked, ‘What’s an atom?’ To my third grader’s mind, the question betrayed a level of ignorance more befitting a preschooler, but the teacher disagreed and banned me from recess for a week. I had forgotten the incident until a few years ago, while sitting in on a quantum mechanics class taught by a Nobel Prizewinning physicist. Midway through a brutally abstract lecture on the hydrogen atom, a plucky sophomore raised his hand and asked the very same question. To the astonishment of all, our speaker fell silent. He stared out the window for what seemed like an eternity before answering, ‘I don’t know.’

They say that the best weapon is the one you never have to fire. I respectfully disagree. I prefer the weapon you only have to fire once. That’s how Dad did it, that’s how America does it... and it’s worked out pretty well so far. I present to you the newest in Stark Industries’ Freedom line. Find an excuse to let one of these off the chain, and I personally guarantee, the bad guys won’t even wanna come out of their caves. Ladies and gentlemen, for your consideration... the Jericho.