The play by William Shakespeake, "Othello" has the line: "That men should put an enemy in their mouths to steal away their brains!". These are specific words said by Cassio in Act 2, Scene 3.

The quote in this instance has been interpreted by a good group of literary scholars. They point out that Cassio is remembering some impressions as an untidy collection or pile of vague images (pictures). Nothing distinctly is recalled by Cassio. He can remember a fight, but not why any of the men are fighting. He would subsequently ask, "Oh God, why do men drink and lose their minds? Why do we party until we’re like wild animals?".

To sum it up for Cassio, his idea is that alcohol is a thief that steals one's brains. So why stick the thief (alcohol) so near your brains (i.e., in your mouth).

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