Most of the ideas within Theology are ideas that went on to become known as Philosophy (for proof: Christian theology came after Philosophy but Aristotle was regarded as the authority on basically everything for pre-Reformation theologians, despite him not being a Christian or having anything to with Christianity...this also occurred in Judaism and Islam).

There are obviously topics that are fairly inseparable from religion, for example hermeneutics, but religion is just another frame of reference onto all the issues that are still important to humans today. Whether you believe that God exists or not is usually not particularly relevant, you just believe the eventual cause is different.