In reply to the critics who claim Christianity was just a copy-cat religion among the ancient religions, it's helpful to take a look at how an ancient adherent of these pagan religions viewed Christianity. The inherent uniqueness of Christianity was a scandal to many. Not only would Jesus' followers not worship other gods, they rejected the layers of intermediary deities. Christianity taught that we could approach God directly in Jesus Christ. This was utterly unique in the ancient pantheon of gods.
This passage from David Bentley Hart's book Atheist Delusions, recounts such reaction and makes an interesting parallel to one of the most common contemporary objections.
In such a world [the polytheism and syncretism of ancient Rome], the gospel was an outrage, and it was perfectly reasonable for its cultured despisers to describe its apostles as “atheists.” Christians were – what could be more obvious? – enemies of society, impious, subversive, and irrational; and it was no more than civic prudence to detest them for refusing to honor the gods of their ancestors, for scorning the common good, and for advancing the grotesque and shameful claim that all the gods and spirits had been made subject to a crucified criminal from Galilee – one who during his life had consorted with peasants and harlots, lepers and lunatics. This was far worse than mere irreverence; it was pure and misanthropic perversity; it was anarchy. One can see something of this alarm in the fragments we still possess of On True Doctrine by the second-century pagan Celsus (preserved in Origen’s treatise Against Celsus, written many decades later). It is unlikely that Celsus would have thought the Christians worth his notice had he not recognized something uniquely dangerous lurking in their gospel of love and peace. He would have naturally viewed the new religion with a certain patrician disdain, undoubtedly, and his treatise contains considerable quantity of contempt for the ridiculous rabble and pliable simpletons that Christianity attracted into its fold: the lowborn and uneducated, slaves, women and children, cobblers, laundresses, weavers of wool, and so forth. But, at that level, Christianity would have been no more distasteful to Celsus than any of those other Asiatic superstitions that occasionally course through the empire, working mischief in every social class, and provoking a largely impotent consternation from the educated and well bred. It would hardly have merited the energetic attack he actually wrote.
What clearly and genuinely horrified Celsus about this particular superstition was not its predictable vulgarity but the novel spirit of rebellion that permeated its teachings. He continually speaks of Christianity as a form of sedition or rebellion, and what he principally condemns is its defiance of the immemorial religious customs of the world’s tribes, cities, and nations. The several peoples of the earth, he believed, were governed by various gods who acted as lieutenants of the Great God, and the laws and customs they had established in every place were part of the divine constitution of the universe, which no one, high born or low, should presume to disregard or abandon. It was appalling to him that Christians, feeling no decent reverence for these ancient ordinances and institutions, should refrain from worship of the gods, should decline to venerate the good daemons who served as intermediaries between the human and divine worlds, and should even refuse to pray to these ancient powers for the emperor. These Christians were so depraved as to think themselves actually above the temples and traditions and cults of their ancestors; they even – ludicrously enough – imagined themselves somehow to have been raised above the deathless emissaries of God, the divine stars and all the other celestial agencies, and to have been granted a kind of immediate intimacy with God himself. And in thus claiming emancipation from the principalities and powers, the thrones and dominions, they had also renounced their spiritual and moral ties to their peoples and to the greater cosmic order. To Celsus, this was all too clearly an unnatural and deracinated piety, a religion like no other, which – rather than providing a sacred bond between the believer and his nation – sought to transcend nations altogether.
And, of course, he was entirely correct. The Christians were indeed a separate people, or at least aspired to be: another nation within each nation (as Origin liked to say), a new humanity that (according to Justin Martyr) had learned no longer to despise those of other races but rather to live with them as brothers and sisters. The church – governed by its own laws, acknowledging no rival allegiances – aimed at becoming a universal people, a universal race, more universal than any empire of gods or men, and subject only to Christ. No creed could have been more subversive of the ancient wisdom of the world, and no movement more worthy of the hatred of those for whom that wisdom was the truth of the ages.
One of the more diverting ironies of contemporary anti-Christian polemic is the recrudescence of this same line of critique – or, rather, the development of something very similar, though with a more modern inflection. Today, obviously, it is not the “seditiousness” of the gospel that offends us (we are scarcely conscious of it), much less its “vulgarity” (which for us is a word almost devoid of any connotation of disapproval), but its “intolerance.” At least, in certain circles, this has become a favorite complaint. It is needless to say, a charge redolent of certain distinctly modern concerns. The early Christians rarely would have had the leisure to think in such terms, even had those terms been intelligible to then. As theirs was for centuries the weaker position within society, they tended to think of the faiths of their ancestors not simply as rival creeds but as a tyranny from which they had escaped. They understood their rejection of all gods but their own as the very charter of their spiritual freedom, their writ of emancipation from the malign cosmic principalities that enslaved the nations. To judge from some of the recent popular literature on the topic, however, there are some who view this attitude on the part of the early Christians not only as unreasonable, nor only as a little wicked, but as Christianity’s principal and most damning fault.