An open flatterer any one can detect, unless he is an absolute fool the covert insinuation of the cunning and the sly is what we have to be studiously on our guard against.
 Marcus Tullius Cicero, On Friendship (44 BC). copy citation

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Author Marcus Tullius Cicero
Source On Friendship
Topic absolute detecting
Date 44 BC
Language English
Reference
Note Translated by E. S. Shuckburgh
Weblink http://www.gutenberg.org/files/2808/2808-h/2808-h.htm

Context

“Wherefore, though it is with those who catch at and invite it that this flattering falsehood is especially powerful, yet men even of soldier and steadier character must be warned to be on the watch against being taken in by cunningly disguised flattery. An open flatterer any one can detect, unless he is an absolute fool the covert insinuation of the cunning and the sly is what we have to be studiously on our guard against. His detection is not by any means the easiest thing in the world, for he often covers his servility under the guise of contradiction, and flatters by pretending to dispute, and then at last giving in and allowing himself to be beaten, that the person hoodwinked may think himself to have been the clearer-sighted.” source