Dear atheists and agnostics, I see religion as the proverbial “elephant” studied by the “six blind men“: a philosopher, an ethicist, a psychologist, an anthropologist, a sociologist, an evolutionist (of the Dawkins or D. S. Wilson kind), a historian (sorry, that makes seven). They all can agree that there indeed is a phenomenon called religion but are confused about what is its purpose or why it is there at all; that is, unless they have an indwelling knowledge of it (Polanyi) through faith.
Taking the philosopher‘s point of view (but always aware of the six others) there are in principle only two presuppositions, hypotheses: Either - as Carl Sagan put it - the physical universe is all there is, without cause and without purpose (”nobody created it”), or there must be Something (different religions model It differently, we call Him God) not reducible to the physical universe, which has no cause and no purpose but is the carrier of the cause and purpose of the physical universe.
There is no rational way to decide a priori in favour of the one or the other presupposition. There are only arguments, including rational ones, that can support one’s preconceived preference. One of them might be the Occam‘s razor principle that would favour Sagan. For a believer his/her preference comes from some of the realms of interest to the other “blind men”, like a personal (religious) experience or just simple marvel at the world around him/her that he/she simply cannot accept as being without cause and without purpose, combined with education and cultural environment. However, one cannot convey this experience, this marvel and admiration for the Creator, to an atheist or agnostic who for whatever reasons has no sense of it. Like you cannot convey to a blind man the beauty of a sunset, or to a deaf man that of a nice piece of music.
Of course, a Christian’s belief system is richer than just a rejection of the Sagan alternative. The case of non-Euclidean geometry can illustrate that there is not such a big difference between axioms as understood by contemporary mathematicians, and a Catholic‘s “axioms“ or “articles of faith“ understood as “necessary truths”: Until about 1800 the Euclidean axioms were understood even by mathematicians as “necessary truths”, since they were convinced that Euclidean geometry was the only correct idealisation of the properties of physical space. Today no mathematician speaks of axioms as necessary truths any more. In case of metaphysical/religious models of reality the situation is more complicated: for a believer his/her “axioms“ are even today “necessary truths”; for an unbeliever they deal with undefined concepts. So in a certain sense, to ask a believer to prove (give evidence for) the articles of faith his/her belief system is built on is like asking a mathematician to prove the axioms he builds his/her theory on.