Justin Martyr was a 2nd century apologist, and is considered as one of the Apostolic fathers in church history. His writings, along with many of the Ante-Nicene fathers, which means prior to the council of Nicaea in 325 AD, were highly influential on the early church and continue to encourage Christians today. Justin Martyr wrote an important work which is titled First Apology, where he addresses Antoninus Pius, his sons, and the Roman Senate in which Justin gives an apology, or defense, of the Christian faith. Particularly, Justin responds to the accusations of Christians being atheists in chapters 4 through 6.
Here is chapter 4 of Justin Martyr’s First Apology:
Chapter IV.—Christians unjustly condemned for their mere name.
By the mere application of a name, nothing is decided, either good or evil, apart from the actions implied in the name; and indeed, so far at least as one may judge from the name we are accused of, we are most excellent people. But as we do not think it just to beg to be acquitted on account of the name, if we be convicted as evil-doers, so, on the other hand, if we be found to have committed no offence, either in the matter of thus naming ourselves, or of our conduct as citizens, it is your part very earnestly to guard against incurring just punishment, by unjustly punishing those who are not convicted. For from a name neither praise nor punishment could reasonably spring, unless something excellent or base in action be proved. And those among yourselves who are accused you do not punish before they are convicted; but in our case you receive the name as proof against us, and this although, so far as the name goes, you ought rather to punish our accusers. For we are accused of being Christians, and to hate what is excellent (Chrestian) is unjust. Again, if any of the accused deny the name, and say that he is not a Christian, you acquit him, as having no evidence against him as a wrong-doer; but if any one acknowledge that he is a Christian, you punish him on account of this acknowledgment. Justice requires that you inquire into the life both of him who confesses and of him who denies, that by his deeds it may be apparent what kind of man each is. For as some who have been taught by the Master, Christ, not to deny Him, give encouragement to others when they are put to the question, so in all probability do those who lead wicked lives give occasion to those who, without consideration, take upon them to accuse all the Christians of impiety and wickedness. And this also is not right. For of philosophy, too, some assume the name and the garb who do nothing worthy of their profession; and you are well aware, that those of the ancients whose opinions and teachings were quite diverse, are yet all called by the one name of philosophers. And of these some taught atheism; and the poets who have flourished among you raise a laugh out of the uncleanness of Jupiter with his own children. And those who now adopt such instruction are not restrained by you; but, on the contrary, you bestow prizes and honours upon those who euphoniously insult the gods.
Chapter V.—Christians charged with atheism.
Why, then, should this be? In our case, who pledge ourselves to do no wickedness, nor to hold these atheistic opinions, you do not examine the charges made against us; but, yielding to unreasoning passion, and to the instigation of evil demons, you punish us without consideration or judgment. For the truth shall be spoken; since of old these evil demons, effecting apparitions of themselves, both defiled women and corrupted boys, and showed such fearful sights to men, that those who did not use their reason in judging of the actions that were done, were struck with terror; and being carried away by fear, and not knowing that these were demons, they called them gods, and gave to each the name which each of the demons chose for himself. And when Socrates endeavoured, by true reason and examination, to bring these things to light, and deliver men from the demons, then the demons themselves, by means of men who rejoiced in iniquity, compassed his death, as an atheist and a profane person, on the charge that “he was introducing new divinities;” and in our case they display a similar activity. For not only among the Greeks did reason (Logos) prevail to condemn these things through Socrates, but also among the Barbarians were they condemned by Reason (or the Word, the Logos) Himself, who took shape, and became man, and was called Jesus Christ; and in obedience to Him, we not only deny that they who did such things as these are gods, but assert that they are wicked and impious demons, whose actions will not bear comparison with those even of men desirous of virtue.
Chapter VI.—Charge of atheism refuted.
Hence are we called atheists. And we confess that we are atheists, so far as gods of this sort are concerned, but not with respect to the most true God, the Father of righteousness and temperance and the other virtues, who is free from all impurity. But both Him, and the Son (who came forth from Him and taught us these things, and the host of the other good angels who follow and are made like to Him), and the prophetic Spirit, we worship and adore, knowing them in reason and truth, and declaring without grudging to every one who wishes to learn, as we have been taught.