Science is the process of determining the behavior of matter (the universe) using observation, testing (controlled observation), and reason; with reason defined as the ability to observe, comprehend and accept self-evident truth.
[Reason is] “the discovery of the certainty or probability of such propositions or truths, which the mind arrives at by deduction made from such ideas, as it has got by the use of its natural faculties…” — John Locke
Faith is any belief based on that which is unobservable and un-testable, which is to say any belief which is undiscoverable by science, which is to say any belief beyond the discovery of reason.
“Where revelation comes into its own is where reason cannot reach. Where we have few or no ideas for reason to contradict or confirm, this is the proper matters for faith… that Part of the Angels rebelled against GOD, and thereby lost their first happy state: and that the dead shall rise, and live again: These and the like, being beyond the discovery of reason, are purely matters of faith; with which reason has nothing to do.” — John Locke
Religion contains faith that an eternal God created matter (the universe) with a finite beginning at the Big Bang – a supernatural belief not based on direct observation of that which preceded creation. If the universe was not created by God, then where did it come from? We know from the law of conservation of energy that without outside force neither mass nor energy can create its self, nor can mass or energy be destroyed; the sum of mass and energy is always constant in any closed system including the universe it’s self. Mass can be converted into energy, and visa-versa, so mass and energy are limited to interchangeability (E = MC2), but according to the law of conservation of energy only nothing can come from nothing. According to the most fundamental law of science a self-created universe is an un-scientific belief – an irrational belief.
It is self-evident that if the universe was not created by God, and since it did not create its self, and since it cannot be destroyed, it must be eternal in time, both in the past and in the future – possibly an infinite series of Big Bangs – or a universe in rotation around an eternally old ultra-massive black hole at its center. The most basic law of science tells us that outside power is a requirement for the creation of nature’s mass and energy, so we are left with either an eternal un-created God with no beginning and no end who created our finite universe with a Big Bang (religion), or we have an eternal un-created universe with no beginning and no end (atheism).
Since faith is any belief based on that which is unobservable, such as belief in God, and since no one was or could be present to observe the beginning of a Universe with no beginning, belief in an eternal un-created universe (atheism) is based on faith. Here we have the irreducible basis for both religious and atheist belief. Adherence to the law of conservation of energy does not require us to choose one belief over the other – it simply requires that one must be true and one false. Both religion and atheism represent leaps of faith equal in magnitude but opposite in direction – two mutually exclusive beliefs – each beyond the discovery of reason.