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.

Every man hath a good and a bad angel attending on him, all his life long.

Naught so sweet as melancholy.

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

Temperance is a bridle of gold; he, who uses it rightly, is more like a god than a man.

Ignorance is the Mother of Devotion.

Properly conducted scientific studies . . . give us a pretty good idea of when something is likely to be correct. To me, pretty good is a linguistic statistic that falls somewhere in between more likely than not and beyond a reasonable doubt, et avoides the pitfalls arising from the belief in complete objectivity.