Faith is not just a religious word, nor does it deal only with God. To say you believe in inflation theory is to say you have faith that it's true. Faith is not without it's reasons. We exercise faith because we are "finite" not because we are religious.
All world views are pre-suppositional. I can't "empirically" prove that God exists. I can't prove there is no God nor that everything is God. I can't prove that there is life after death. I can't prove that we reincarnate or that we cease to exist.
To say all that exists is nature is as much a presupposition as saying all that exists is God. To say there are multi-universes or only one universe...
you get the point?
Science has it's apologetics as well as religion. Cosmic microwave background is used in defense or support of inflation theory.
"Metaphysical naturalism, also called ontological naturalism, philosophical naturalism and scientific materialism is a strong belief in naturalism, a worldview with a philosophical aspect which holds that there is nothing but natural elements, principles, and relations of the kind studied by the natural sciences, i.e., those required to understand our physical environment by mathematical modeling. In contrast, methodological naturalism is an assumption of naturalism as a methodology of science, for which metaphysical naturalism provides only one possible ontological foundation.
Metaphysical naturalism holds that all properties related to consciousness and the mind are reducible to, or supervene upon, nature. Broadly, the corresponding theological perspective is religious naturalism or spiritual naturalism. More specifically, metaphysical naturalism rejects the supernatural concepts and explanations that are part of many religions."--Wiki
--Dave