Some sentence that began “It is impossible not to ignore” went past me on the radio while I was half asleep yesterday. By the time I started thinking about the sentence, I’d lost the context, but it seemed very likely that the sentence was an instance of overnegation, probably intended to convey ‘it is impossible to ignore’, but with an extra negative element, the explicit negator not (in addition to impossible and ignore, where the negation is “incorporated” into a word). Language Log has been looking at overnegations (and undernegations) for some time — an inventory of postings on overnegation, up through 5/18/07, can be found here — but “impossible not to ignore” seems not to have been recorded there (though other overnegation types with impossible or ignore in them have been). So this posting is a modest addition to the overnegation literature.