Rationality Quotes August 2013

Another month has passed and here is a new rationality quotes thread. The usual rules are:

Please post all quotes separately, so that they can be upvoted or downvoted separately. (If they are strongly related, reply to your own comments. If strongly ordered, then go ahead and post them together.)
Do not quote yourself.
Do not quote from Less Wrong itself, HPMoR, Eliezer Yudkowsky, or Robin Hanson. If you'd like to revive an old quote from one of those sources, please do so here.
No more than 5 quotes per person per monthly thread, please.

Another month has passed and here is a new rationality quotes thread. The usual rules are:

Please post all quotes separately, so that they can be upvoted or downvoted separately. (If they are strongly related, reply to your own comments. If strongly ordered, then go ahead and post them together.)
Do not quote yourself.
Do not quote from Less Wrong itself, HPMoR, Eliezer Yudkowsky, or Robin Hanson. If you'd like to revive an old quote from one of those sources, please do so here.
No more than 5 quotes per person per monthly thread, please.

It ain’t ignorance [that] causes so much trouble; it’s folks knowing so much that ain’t so.

Josh Billings

Famously subverted by Ronald Reagan as:

The trouble with our liberal friends is not that they are ignorant, but that they know so much that isn't so.

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