A blinking idiot
What's here? the portrait of a blinking idiot,
Presenting me a schedule! I will read it.
How much unlike art thou to Portia!
How much unlike my hopes and my deservings!
"Who chooseth me shall have as much as he deserves"!
Did I deserve no more than a fool's head?
Is that my prize? Are my deserts no better?
Portia:The Merchant Of Venice Act 2, scene 9, 54–62
To offend and judge are distinct offices,
And of opposed natures.
The beautiful, wealthy, and orphaned Portia has attracted the attention of a number of noble bachelors. But according to her father's will, she can give her hand in marriage only to the suitor who chooses the one of three caskets which contains a small picture of the lady herself. Each casket is made of a different metal—gold, silver, or lead—and comes with an appropriate motto. The arrogant and appropriately named Prince of Arragon, responding to the motto "Who chooseth me shall have as much as he deserves," selects the silver casket, and finds therein a picture not of Portia, but of "a blinking idiot," a "fool's head," or dolt. When he protests that, surely, he deserves better than this, Portia replies stingingly that the offender is not an appropriate judge of his own case.
"Blinking" here can mean "winking," but there's no way what we mean by "blinking" could be represented in a picture. The idiot must be squinting his eyes, or have one open and one closed. In any case, it is sufficiently clear that the blockhead likened to Arragon has weak eyes, and therefore, metaphorically, weak perception. This judgment is reflected in our use of the phrase, even while we don't insist on any specific meaning at all for "blinking."
Themes: insults and slander