I wish, however, to show how Celsus asserts without any good reason, that each one reveres his domestic and native institutions. For he declares that “those Ethiopians who inhabit Meroe know only of two gods, Jupiter and Bacchus, and worship these alone; and that the Arabians also know only of two, viz., Bacchus, who is also an Ethiopian deity, and Urania, whose worship is confined to them.” According to his account, neither do the Ethiopians worship Urania, nor the Arabians Jupiter.
If, then, an Ethiopian were from any accident to fall into the hands of the Arabians, and were to be judged guilty of impiety because he did not worship Urania, and for this reason should incur the danger of death, would it be proper for the Ethiopian to die, or to act contrary to his country's laws, and do obeisance to Urania? Now, if it would be proper for him to act contrary to the laws of his country, he will do what is not right, so far as the language of Celsus is any standard; while, if he should be led away to death, let him show the reasonableness of selecting such a fate.
I know not whether, if the Ethiopian doctrine taught men to philosophize on the immortality of the soul, and the honour which is paid to religion, they would reverence those as deities who are deemed to be such by the laws of the country. A similar illustration may be employed in the case of the Arabians, if from any accident they happened to visit the Ethiopians about Meroe. For, having been taught to worship Urania and Bacchus alone, they will not worship Jupiter along with the Ethiopians; and if, adjudged guilty of impiety, they should be led away to death, let Celsus tell us what it would be reasonable on their part to do.
And with regard to the fables which relate to Osiris and Isis, it is superfluous and out of place at present to enumerate them. For although an allegorical meaning may be given to the fables, they will nevertheless teach us to offer divine worship to cold water, and to the earth, which is subject to men, and all the animal creation. For in this way, I presume, they refer Osiris to water, and Isis to earth; while with regard to Serapis the accounts are numerous and conflicting, to the effect that very recently he appeared in public, agreeably to certain juggling tricks performed at the desire of Ptolemy, who wished to show to the people of Alexandria as it were a visible god.
And we have read in the writings of Numenius the Pythagorean regarding his formation, that he partakes of the essence of all the animals and plants that are under the control of nature, that he may appear to have been fashioned into a god, not by the makers of images alone, with the aid of profane mysteries, and juggling tricks employed to invoke demons, but also by magicians and sorcerers, and those demons who are bewitched by their incantations.
Source: Against Celsus (New Advent)