4 As regards the worship of the Almighty God, you might call us a schism of the Jews, for all Jews are bold enough to profess this worship, were it not for the difference in the form of our worship, though it may be questioned whether the Jews really worship the Almighty. But the doctrine I have mentioned is common to the Pagans in their worship of the sun, and to the Jews in their worship of the Almighty. Even in relation to you, we are not properly a schism, though we acknowledge Christ and worship Him; for our worship and doctrine are different from yours.
In a schism, little or no change is made from the original; as, for instance, you, in your schism from the Gentiles, have brought with you the doctrine of a single principle, for you believe that all things are of God. The sacrifices you change into love-feasts, the idols into martyrs, to whom you pray as they do to their idols. You appease the shades of the departed with wine and food. You keep the same holidays as the Gentiles; for example, the calends and the solstices. In your way of living you have made no change.
Plainly you are a mere schism; for the only difference from the original is that you meet separately. In this you have followed the Jews, who separated from the Gentiles, but differed only in not having images. For they used temples, and sacrifices, and altars, and a priesthood, and the whole round of ceremonies the same as those of the Gentiles, only more superstitious. Like the Pagans, they believe in a single principle; so that both you and the Jews are schisms of the Gentiles, for you have the same faith, and nearly the same worship, and you call yourselves sects only because you meet separately.
The fact is, there are only two sects, the Gentiles and ourselves. We and the Gentiles are as contrary in our belief as truth and falsehood, day and night, poverty and wealth, health and sickness. You, again, are not a sect in relation either to truth or to error. You are merely a schism and a schism not of truth, but of error.
Source: Reply to Faustus the Manichaean (New Advent)