Deliberately refuse to acknowledge something which you know to be true.
Admiral Horatio Nelson is supposed to have said this when wilfully disobeying a signal to withdraw during a naval engagement. Such tales, especially about national heroes like Nelson, are often exaggerated or fictitious. Here, however, there’s very good evidence to show that Nelson was indeed the source of this phrase.
In the naval battle of Copenhagen in 1801 Nelson led the attack of the British fleet against a joint Danish/Norwegian enemy. The British fleet of the day was commanded by Admiral Sir Hyde Parker. The two men disagreed over tactics and at one point Hyde Parker sent a signal (by the use of flags) for Nelson to disengage. Nelson was convinced he could win if he persisted and that’s when he ‘turned a blind eye.’
In a biography Life of Nelson, published only eight years later, Clarke and M’Arthur printed what they claimed to be Nelson’s actual words at the time:
[Putting the glass to his blind eye] “You know, Foley, I have only one eye – and I have a right to be blind sometimes. I really do not see the signal.”
The first recorded use of the phrase as we normally use it today is in More letters from Martha Wilmot: impressions of Vienna, 1819-1829. This was reprinted in 1935 and the following quotation is recorded as being sent by Ms. Wilmot in 1823:
“turn a blind eye and a deaf ear every now and then, and we get on marvelously well.”
Martha Wilmot had it right, I think. In order to keep the peace, we all turn a blind eye and a deaf ear to our nearest and dearest now and then, as well as all the rest of humanity.