“It is a mistake always to contemplate the good and ignore the evil, because by making people neglectful it lets in disaster. There is a dangerous optimism of ignorance and indifference.”

Source: All I Need Is You

Source: Fool's Fate

Re: is CLOS reall OO? http://groups.google.com/group/comp.lang.lisp/msg/917737b7cc8510e3 (Usenet article).
Usenet articles, C++

The words of Socrates, as quoted by Diogenes Laertius.
Misattributed

The Plague (1947)
Context: The evil that is in the world always comes of ignorance, and good intentions may do as much harm as malevolence, if they lack understanding. On the whole men are more good than bad; that, however, isn't the real point. But they are more or less ignorant, and it is this that we call vice or virtue; the most incorrigible vice being that of an ignorance which fancies it knows everything and therefore claims for itself the right to kill. There can be no true goodness, nor true love, without the utmost clear-sightedness.

Socrates II: xxxi http://www.perseus.tufts.edu/hopper/text?doc=D.+L.+2.5.31&fromdoc=Perseus%3Atext%3A1999.01.0257#note-link14. Original Greek: ἓν μόνον ἀγαθὸν εἶναι, τὴν ἐπιστήμην, καὶ ἓν μόνον κακόν, τὴν ἀμαθίαν
Diogenes Laertius
Variant: The only good is knowledge and the only evil is ignorance.

Source: Annie on My Mind

Poems (1964), Preface.