Those who have taken upon them to lay down the law of nature as a thing already searched out and understood, whether they have spoken in simple assurance or professional affectation, have therein done philosophy and the sciences great injury. For as they have been successful in inducing belief, so they have been effective in quenching and stopping inquiry; and have done more harm by spoiling and putting an end to other men's efforts than good by their own.
--From The New Organon--
Looking at 1620 from the present it's obvious how people being sure they knew certain "truths" was a problem, especially truths we now consider false. But what errors are we preserving in our own textbooks, today?