Live and act within the limit ...

Live and act within the limit of your knowledge and keep expanding it to the limit of your life. Redeem your mind from the hockshops of authority. Accept the fact that you are not omniscient, but playing a zombie will not give you omniscience-that your mind is fallible, but becoming mindless will not make you infallible-that an error made on your own is safer than ten truths accepted on faith, because the first leaves you the means to correct it, but the second destroys your capacity to distinguish truth from error.
Live and act within the limit of your knowledge and keep expanding it to the limit of your life. Redeem your mind from the hockshops of authority. Accept the fact that you are not omniscient, but playing a zombie will not give you omniscience-that your mind is fallible, but becoming mindless will not make you infallible-that an error made on your own is safer than ten truths accepted on faith, because the first leaves you the means to correct it, but the second destroys your capacity to distinguish truth from error.
 Ayn Rand

Quotes from the same author

A creative man is motivated by the desire to achieve, not by the desire to beat others.
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 Ayn Rand
The truth is not for all men, but only for those who seek it.
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 Ayn Rand
The action required to sustain human life is primarily intellectual; everything man needs has to be discovered by his mind and produced by his effort.
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 Ayn Rand
If you want to know the one reason that's taking me back, I'll tell you: I cannot bring myself to abandon to destruction all the greatness of the world, all that which was mine and yours, which was made by us and is still ours by right - because I cannot believe that men refuse to see, that they can remain blind and deaf to us forever, when the truth is ours and their lives depend on accepting it.
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 Ayn Rand
Run for your life from any man who tells you that money is evil. That sentence is the leper's bell of an approaching looter. So long as men live together on earth and need means to deal with one another--their only substitute, if they abandon money, is the muzzle of a gun.
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 Ayn Rand