On Idolatry by Tertullian
Chapter XX.--Concerning Idolatry in Words.
But, however, since the conduct according to the divine rule is imperilled, not merely by deeds, but likewise by words, (for, just as it is written, |Behold the man and his deeds;| so, |Out of thy own mouth shalt thou be justified| ), we ought to remember that, even in words, also the inroad of idolatry must be foreguarded against, either from the defect of custom or of timidity. The law prohibits the gods of the nations from being named, not of course that we are not to pronounce their names, the speaking of which common intercourse extorts from us: for this must very frequently be said, |You find him in the temple of Æsculapius;| and, |I live in Isis Street;| and, |He has been made priest of Jupiter;| and much else after this manner, since even on men names of this kind are bestowed. I do not honour Saturnus if I call a man so, by his own name. I honour him no more than I do Marcus, if I call a man Marcus. But it says, |Make not mention of the name of other gods, neither be it heard from thy mouth.| The precept it gives is this, that we do not call them gods. For in the first part of the law, too, |Thou shalt not,| saith He, |use the name of the Lord thy God in a vain thing,| that is, in an idol. Whoever, therefore, honours an idol with the name of God, has fallen into idolatry. But if I speak of them as gods, something must be added to make it appear that I do not call them gods. For even the Scripture names |gods,| but adds |their,| viz. |of the nations:| just as David does when he had named |gods,| where he says, |But the gods of the nations are demons.| But this has been laid by me rather as a foundation for ensuing observations. However, it is a defect of custom to say, |By Hercules, So help me the god of faith;| while to the custom is added the ignorance of some, who are ignorant that it is an oath by Hercules. Further, what will an oath be, in the name of gods whom you have forsworn, but a collusion of faith with idolatry? For who does not honour them in whose name he swears?