For Quintus Roscius the Actor (46)

But what is the difference between a perjurer and a liar? He who is in the habit of lying, is in the habit of perjuring himself. The man whom I can induce to tell a lie, I shall easily be able to prevail on to take a false oath. For he who has once departed from truth, is easily led on, with no greater scruples to perjury than to a lie. For who is influenced by just a mention of the gods in the way of deprecating their anger, and not by the influence of conscience? Because the same punishment which is appointed by the immortal gods for a perjurer is appointed also for a liar. For the immortal gods are accustomed to be indignant and angry, not on account of the form of words in which an oath is contained, but on account of the treachery and malice by which a plot is laid to deceive any one.