Circular reasoning is a type of logical fallacy in which the "proof" of a statement ultimately depends on assuming the truth of the statement itself.
- We know that God exists because the Bible says so.
- We know that Bible is correct because it is the inspired word of God.
In other words:
- Bible implies God implies Bible
Neither the assertion that "God exists" nor that "the Bible is correct" have been independently proved without relying on the assumption of the other.
Presuppositional apologists (primarily from the reformed school of theology) argue that circular reasoning is an acceptable and necessary thing within a world-view and that circular reasoning is only un-acceptable when it presents a self-contradiction.
This is demonstrated by showing that the scientific worldview has certain assumptions about the universe and that those assumptions are based on observation but then observation is explained in terms of laws, which are themselves assumptions about the universe. This is, of course, acceptable because it is consistent in and of itself.