If everybody is thinking alike, then somebody isn't thinking.

Si todo el mundo piensa igual es que alguien no está pensando.

Where all think alike, no one thinks very much. — WALTER LIPPMANN, The Stakes of Diplomacy

If we all think alike, no one is thinking.

It would be a dull world if we all thought alike.

Não tenha medo de pensar diferente dos outros, tenha medo de pensar igual e descobrir que todos estão errados.

Nobody is thinking about you the way you are thinking about you. They’re all thinking about themselves.

Those who talk about individuality the most are the ones who most object to deviation, and in a few years it may be the other way around. Some day everybody will just think what they want to think, and then everybody will probably be thinking alike; that seems to be what is happening.

Everybody's the same. People are all the same. But it’s the prerogative of youth to think it’s not so.

[...] the diversity of our opinions, consequently, does not arise from some being endowed with a larger share of reason than others, but solely from this, that we conduct our thoughts along different ways, and do not fix our attention on the same objects. For to be possessed of a vigorous mind is not enough; the prime requisite is rightly to apply it. The greatest minds, as they are capable of the highest excellences, are open likewise to the greatest aberrations; and those who travel very slowly may yet make far greater progress, provided they keep always to the straight road, than those who, while they run, forsake it.

there are very few who can think, but every man wants to have an opinion; and what remains but to take it ready-made from others, instead of forming opinions for himself?

Everybody is very much alike, really. But fortunately, perhaps, they don't realise it. - Miss Marple

If people cannot write well, they cannot think well, and if they cannot think well, others will do their thinking for them.

all the while I was thinking that I was the only man who did not know what I was about, and that all the others did — whereas, as I found out later, pretty much everybody else was as much in the dark as I was.