In short, we repudiated all versions of the doctrine of original sin, of there being insane and irrational springs of wickedness in most men. We were not aware that civilization was a thin and precarious crust erected by the personality and the will of a very few, and only maintained by rules and conventions skillfully put across and guilefully preserved. We had no respect for traditional wisdom or the restraints of custom. We lacked reverence ... for everything and everyone. It did not occur to us to respect the extraordinary accomplishment of our predecessors in the ordering of life (as it now seems to me to have been) or the elaborate framework which they had devised to protect this order. ... As cause and consequence of our general state of mind we completely misunderstood human nature, including our own. The rationality which we attributed to it led to a superficiality, not only of judgement, but also of feeling.
author: John Maynard Keynes
Although Keynes showed some willingness to change his mind when the facts changed, his near certitude expressed on many matters left me in the position of being rather stunned to learn of this quote. It is particularly relevant for the conflict of visions that are at the heart of many disagreements that underlay policy differences and differing attitudes towards the desirability of limited government.
A slightly more extended excerpt is here. A video from which I became aware of this quote is here (with a slightly extended version of the quote starting around 18:00).