Eclecticism

Eclecticism is the theory or practice of an eclectic method, which itself is defined by Merriam-Webster as follows:

1 : selecting what appears to be best in various doctrines, methods, or styles
2: composed of elements drawn from various sources

Source: eclectic Merriam-Webster Online

Compare with syncretism, which is "the combination of different forms of belief or practice."

See Also