...we cannot foresee which parts of our scientific knowledge may come to grief one day. Thus the belief in scientific certainty and in the authority of science is just wishful thinking: science is fallible, because science is human.
But the fallibility of our knowledge—or the thesis that all knowledge is guesswork, though some consists of guesses which have been most severely tested—must not be cited in support of scepticism or relativism. From the fact that we can err, and that a criterion of truth which might save us from error does not exist, it does not follow that the choice between theories is arbitrary, or non-rational: that we cannot learn, or get nearer to the truth: that our knowledge cannot grow.
— Karl Popper, The Open Society and Its Enemies