Philosophy of religionPhilosophy of religion is the study of the meaning and justification of fundamental religious claims, particularly about the nature and existence of God. Philosophy of religion as part of metaphysics Philosophy of religion was classically regarded as part of metaphysics, since Aristotle, in some of whose writings were later identified by editors as The Metaphysics, described one of the subjects of his investigation as the investigation of first causes. For Aristotle, God was the first cause, the Unmoved Mover. Philosophy of religion as a branch of metaphysics later came to be called, by rationalist philosophers of the seventeenth and eighteenth centuries, natural theology. In the twentieth century, philosophers have adopted the name "philosophy of religion" for the subject, and typically it is regarded as a separate field of specialization, but it is also sometimes still treated as part of metaphysics, particularly by Catholic philosophers. On nearly anyone's conception, it should be clear why considerations of the divine have been regarded as metaphysical. God, according to most conceptions of God of the divine, would be in an important category of being different from the rest of the universe. That is, God is typically conceived as not having a body, and the "mind" of the divine is not typically regarded as anything very like an ordinary human mind. Metaphysics, and in particular ontology, is concerned with the most basic categories of existence, those types of existence that cannot be explained as any other type of existence. On the view of many, the very notion of God (the gods, the divine) cannot be reduced to human concepts of mind or body; God is, on such a view, a sui generis entity, an entity in a category all of its own. The questions asked by the philosophy of religion There are a lot of philosophical questions that can be asked about religious beliefs. But there are two central questions in this field. They are: 1. What is God, that is, what is the meaning of the word, 'God'? 2. Do we have any good reason to think that God exists, or to think that God does not exist? Still, there are other questions studied in the philosophy of religion. What, if anything, would be good reason to believe that a miracle has occurred? What is the relationship between faith and reason? What might it mean for God to be exist as a trinity, that is as the "Father, Son, and Holy Ghost" of Christian theology? Monotheistic definitions Traditionally philosophers of religion, at least in Europe, were interested in finding out what the word "God" might refer to, in the sense in which it is used by theists. Again, theism, can be defined as the view that exactly one God exists, who is an eternally existent spirit, that exists apart from space and time, which has created the universe out of nothing, and is therefore all-powerful; and usually this being is also thought to be all-knowing and all-loving. Even once the word "God" is defined in this sense, there are still many difficult questions to be asked about what this means. For example, what does it mean for a spirit to create anything? What does "all-powerful" mean?