Responsibility was our cruel mooring.... - David Brin

Learn to control ego. Humans hold their dogmas and biases too tightly, and we only think that our opponents are dogmatic! But we all need criticism. Criticism is the only known antidote to error.

There were times when Robert actually envied his ancestors, who had lived in dark ignorance, before the twenty-first century, and seemed to have spent most of their time making up weird, ornate explanations of the world to fill the yawning gap of their ignorance. Back then, one could believe in anything at all.
Simple, deliciously elegant explanations of human behavior—it apparently never mattered whether they were true or not, as long as they were incanted right. "Party lines" and wonderful conspiracy theories abounded. You could even believe in your own sainthood if you wanted. Nobody was there to show you, with clear experimental proof, that there was no easy answer, no magic bullet, no philosopher's stone. Only simple, boring sanity.
How narrow the Golden Age looked in retrospect.

Men can be brilliant and strong, they whispered to one another. But men can be mad, as well. And the mad ones can ruin the world.