“The very corner-stone of an education intended to form great minds, must be the recognition of the principle, that the object is to call forth the greatest possible quantity of intellectual power, and to inspire the intensest love of truth: and this without a particle of regard to the results to which the exercise of that power may lead, even though it should conduct the pupil to opinions diametrically opposite to those of his teachers.” (John Stuart Mill, excerpt from Civilization, published in Westminster Review, 1836)
Related: Mill’s two-decades-later fuller argument for liberal education, independence of mind, and freedom of expression, in his classic On Liberty. In the Philosophers, Explained series.