According to wiki: "Religious syncretism is: A] the blending of two or more belief systems into a new system, or B] the incorporation into a religious tradition of beliefs from unrelated traditions." Alongside this we have religious assimilation, which is something different. Today, in atheist-critical circles, the idea of snycretism is bandied about without interrogation and without distinction. It's an easy way to discredit a belief system by suggesting that because two ideas existed, even contemporaneously, then one must have taken the idea from the other. For example, the Hindu tradition is one of unrestrained assimilation: Jewish, Christian, Moslem, and other religious icons and images decorate Hindu altars, but the Tradition cannot be said to be syncretist — it just assumes that anything good is a manifestation of its 'native' deities, and the incorporation of such does not alter the dogmas or doctrines of Hinduism. The image of Jesus might sit on a Hindu altar, but no Hindu would agree that Jesus alone is the way the truth and the light, or that no-one attains enlightenment but through Him. What you will get is the assurance that Jesus is just a manifestation of a particular Hindu deity. Gnosticism is an early attempt at Christian syncretism, in an attempt to interpret Christian revelation via a dualist worldview that was at odds with the content of Scripture, and introduced gods and demigods, the battle of good v evil, and so on... Syncretism must be distinguished from assimilation, the latter of which refers the ability to incorporate into itself all that is seen as true, good, and beautiful (the transcendentals) in the world. This idea was present in the early church, as we read in the Second Apology of Justin Martyr: "Whatever things were rightly said among all men," says Justin, "are the property of us Christians". Thus, for example, the Golden Rule: "Do to others what you want them to do to you" (Matthew 7:12, Luke 6:31) is found in all moral traditions. Similarly, the seven cardinal vices and virtues existed in the ancient world, although the primary theological virtues were found in Scripture. The Fathers assimilated many of the ideas of Plato, for example. John Meyendorff, the Orthodox theologian said, "when the Fathers thought, they Platonized." But this does not mean they incorporated Plato into Christianity — far from it. Their fundamental assumption was, if Scripture was true, it could be argued logically and rationally, and Plato was the philosophical method of the day. Origen is perhaps the most famous example of someone who was perceived to have overstepped the line from assimilation into sncretism and error, he was condemned for his beliefs, his works reinterpreted through Maximus the Confessor. Arius was another who interpreted Christian revelation through the eyes of Plato. Augustine in his Confessions details how he was a Manichean, a Platonist and finally a Christian. Whilst Thomas Aquinas almost single-handedly re-introduced Aristotle into the West by using his system of argument (thesis-antithesis-aynthesis), he cannot be accused by promoting Aristotle's vision of God or practice of religion. To claim sncretism, one has to demonstrate: A] The 'original' doctrine, or absence thereof, B] The 'alien' doctrine, and C] The change in the basic belief system brought about to accommodate the alien doctrine. The classic case of Rudolf Bultmann's assertion that Christianity is largely a mythology becaus it reads like myth was a standard in Europe when Bultmann was the theological colossus of his day. It has been asserted many times here, but the logic is flawed: A is a myth, B reads like A, therefore B is a myth. Point three does not inevitably follow point two. It's an easy mistake to make, and it's made often.