To this our answer is, that if the Scythians, the nomadic tribes of Libya, the Seres, who according to Celsus have no god, if those other most barbarous and impious nations in the world, and if the Persians even cannot bear the sight of temples, altars, and images, it does not follow because we cannot suffer them any more than they, that the grounds on which we object to them are the same as theirs. We must inquire into the principles on which the objection to temples and images is founded, in order that we may approve of those who object on sound principles, and condemn those whose principles are false.
For one and the same thing may be done for different reasons. For example, the philosophers who follow Zeno of Citium abstain from committing adultery, the followers of Epicurus do so too, as well as others again who do so on no philosophical principles; but observe what different reasons determine the conduct of these different classes. The first consider the interests of society, and hold it to be forbidden by nature that a man who is a reasonable being should corrupt a woman whom the laws have already given to another, and should thus break up the household of another man.
The Epicureans do not reason in this way; but if they abstain from adultery, it is because, regarding pleasure as the chief end of man, they perceive that one who gives himself up to adultery, encounters for the sake of this one pleasure a multitude of obstacles to pleasure, such as imprisonment, exile, and death itself. They often, indeed, run considerable risk at the outset, while watching for the departure from the house of the master and those in his interest. So that, supposing it possible for a man to commit adultery, and escape the knowledge of the husband, of his servants, and of others whose esteem he would forfeit, then the Epicurean would yield to the commission of the crime for the sake of pleasure.
The man of no philosophical system, again, who abstains from adultery when the opportunity comes to him, does so generally from dread of the law and its penalties, and not for the sake of enjoying a greater number of other pleasures. You see, then, that an act which passes for being one and the same— namely, abstinence from adultery— is not the same, but differs in different men according to the motives which actuate it: one man refraining for sound reasons, another for such bad and impious ones as those of the Epicurean, and the common person of whom we have spoken.
Source: Against Celsus (New Advent)