Adherents of different religions generally disagree as to how to best worship God and what is God's plan for mankind, if there is one. There are different approaches to reconciling the contradictory claims of monotheistic religions. One view is taken by exclusivists, who believe they are the chosen people or have exclusive access to absolute truth, generally through revelation or encounter with the Divine, which adherents of other religions do not. Another view is religious pluralism. A pluralist typically believes that his religion is the right one, but does not deny the partial truth of other religions. An example of a pluralist view in Christianity is supersessionism, i.e., the belief that one's religion is the fulfillment of previous religions. A third approach is relativistic inclusivism, where everybody is seen as equally right; an example being universalism: the doctrine that salvation is eventually available for everyone. A fourth approach is syncretism, mixing different elements from different religions. An example of syncretism is the New Age movement.
What is it called when someone belives that their own religion is an advancement of older religions?
supersessionism