Every schoolboy hath that famous testament of Grunnius Corocotta Porcellus at his fingers end.

Certainty and similar states of ‘knowing what we know’ arise out of involuntary brain mechanisms that, like love or anger, function independently of reason.

Good science requires distinguishing between "felt knowledge" and knowledge arising out of testable observations. "I am sure" is a mental sensation, not a testable conclusion. Put hunches, gut feelings, and intuitions into the suggestion box. Let empiric methods shake out the good from bad suggestions.

Certainty is not biologically possible. We must learn (and teach our children) to tolerate the unpleasantness of uncertainty. Science has given us the language and tools of probabilities. We have methods for analyzing and ranking opinion according to their likelihood of correctness. That is enough.

One was never married, and that's his hell; another is, and that's his plague.

Out of too much learning become mad.

No one seriously doubts Socrates' maxim: The unexamined life isn't worth living. Self-assessment and attempts at self-improvement are essential aspects of "the good life." Yes, we should engage in ruthless self-reflection and harsh scrutiny, but we should simultaneously acknowledge that such introspection will, at best, only result in a partial view of our minds at work. Complete objectivity is not an option.