Syncretism is defined as: “the reconciliation or fusion of differing systems of belief.” Religious syncretism often takes place when foreign beliefs are introduced to an indigenous belief system and the teachings are blended and often a blending of multiple different belief systems occurs when philosophies of mankind rise and fall in popularity.

Scripture warns against this practice..

“Take heed to yourself, lest you make a covenant with the inhabitants of the land where you are going, lest it be a snare in your midst.  But you shall destroy their altars, break their sacred pillars, and cut down their wooden images  (for you shall worship no other god, for the Lord, whose name is Jealous, is a jealous God), lest you make a covenant with the inhabitants of the land, and they play the harlot with their gods and make sacrifice to their gods, and one of them invites you and you eat of his sacrifice,  and you take of his daughters for your sons, and his daughters play the harlot with their gods and make your sons play the harlot with their gods.” (Exodus 34:12-16).

A few articles about the issue of syncretism: