Arguments from authority are rarely made by authorities.
Operations of thought are like cavalry charges in a battle — they are strictly limited in number, require fresh horses, and must only be made at decisive moments.
Get-rich-quick schemes do less harm than get-wise-quick ones.
Knowing the answer does not oblige you to raise your hand.
The more unusual the topic, the more conventional the thought it inspires.
If you repress thought sufficiently you need not repress speech.