Philosophical theology is an academic discipline that applies the methods of philosophy to theological concepts, especially but not exclusively Christian beliefs. It may be considered a branch of philosophy of religion, but with an emphasis on specific doctrines. The discipline of theology often speaks in terms that are metaphorical or even mystical, but philosophical theology seeks to clarify these terms in ways more in line with the strict logical or empirical claims of philosophy.
The role of philosophical theology is in some ways to bridge the gap between philosophy of religion and systematic theology. Philosophy of religion seeks to address philosophical or metaphysical concerns, such as whether it is rational to believe in God, what the existence of good and evil says about God, etc. Systematic theology often presupposes the existence of God — even if the theologian does not actually believe in God — and works out the various implications of that or other doctrines. Philosophical theology, on the other hand, uses the systematic approach of philosophy of religion, but applies it to doctrines established by systematic theologians.
For example, many systematic theologians have held for centuries to the doctrine of trinitarian theology, which is the belief that God the Father, God the Son, and God the Holy Spirit are three beings in one. Others, however, might claim that trinitarian theology violates the law of non-contradiction. That means it is inherently illogical to claim that God can be both one and three at the same time. Whereas a systematic or practical theologian might address these concerns in metaphorical terms, a philosophical theologian might seek to use logical or empirical means to prove or disprove the logical viability of trinitarianism.
Critics of philosophical theology can broadly be divided into those that oppose its hyper-rationality and those that claim it fails to address practical aspects of religion. The language of religion and theology has historically been mystical, as seen in doctrines such as trinitarianism or transubstantiation, which is the belief that bread and wine of communion are literally transformed into the body and blood of Christ. According to its critics, philosophical theology's attempt to explain these doctrines in strictly empirical terms does disservice to the inherent mystery of Christian doctrine. Some liberal Christian theologians further criticize this method of theology for being so abstract that it does not engage with practical religious issues, such as social justice or the actual beliefs of religious adherents.