A man who himself does not believe what he tells another … has even less worth than if he were a mere thing. For a thing, as something real and given, has the property of being serviceable. … But the man who communicates his thoughts to someone in words which yet (intentionally) contain the contrary of what he thinks on the subject has a purpose directly opposed to the natural purposiveness of the power of communicating one’s thoughts, and therefore renounces his personality and makes himself a mere deceptive appearance of man, not man himself.

Immanuel Kant (1724-1804) German philosopher

Metaphysics of Morals [Metaphysik der Sitten], “The Doctrine of Virtue [Tugendlehre]” (1797) [tr. Gregor (1964)]