Pythius, therefore, and all others who do one thing while they pretend another are faithless, dishonest, and unprincipled scoundrels. No act of theirs can be expedient, when what they do is tainted with so many vices.
 Marcus Tullius Cicero, On Duties (44 BC). copy citation

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Author Marcus Tullius Cicero
Source On Duties
Topic vice pretending
Date 44 BC
Language English
Reference
Note Translated by Walter Miller
Weblink http://www.constitution.org/rom/de_officiis.htm

Context

“When asked what he meant by "criminal fraud," as specified in these forms, he could reply: "Pretending one thing and practising another" — a very felicitous definition, as one might expect from an expert in making them. Pythius, therefore, and all others who do one thing while they pretend another are faithless, dishonest, and unprincipled scoundrels. No act of theirs can be expedient, when what they do is tainted with so many vices. {61} XV.
But if Aquilius's definition is correct, pretence and concealment should be done away with in all departments of our daily life. Then an honest man will not be guilty of either pretence or concealment in order to buy or to sell to better advantage.” source