Bob Lieblich forwarded this quote from Andrew Sullivan's blog ("Thanks", 8/13/2007), thanking the bloggers who substituted for Sullivan while he was away on vacation:
A moment of sincere and deep thanks to my guest-bloggers this past week. Aaron insisted I stay off the web for the week, and, amazingly, I did, so reading the week's Dish today in one sitting was a great pleasure. Thanks: Liz, Bruce, Stephen and Eric. Enough diversity for a crackling debate at times, but not too much for incoherence. [emphasis added]
This follows the general recipe for overnegation: two or more negatives (one of them within a word), and a meaning that deals with regions on a semantic scale (here the effects of diversity of opinion in various quantities ranging from inadequate to excessive).
To help you think through this particular case, here's an example where everything works:
...enough breeze for sailing, but not too much for comfortable conversation and sight-seeing...
To reframe this phrase along the lines of Sullivan's attempt, we could change it to:
...enough breeze for sailing, but not too much for blowing the roofs off of houses...
Or we could edit Sullivan's phrase so as to limit the cited diversity in a logically correct way:
Enough diversity for a crackling debate at times, but not so much as to lead to incoherence.
Anyhow, Andrew Sullivan knew what he meant, and you probably did too. Our poor old monkey brains are not quite evolved enough for this stuff yet: Multiplex Negatio Ferblondiat.
[Update -- John Cowan writes:
This example reminds me of what James Thurber said Harold Ross said (according to other sources, to Robert Benchley): "I don't want you to think I'm not incoherent". Thurber characterized this overnegation as "[Ross's] limited vocabulary got tangled up in his fluency."
]
Posted by Mark Liberman at August 14, 2007 08:36 AM