I've often been asked how one rationally arrives at a position of atheism - as opposed to say, agnosticism. The recurring questions set me to the task of identifying rationalist principles and then showing that if they were faithfully applied to most theistic claims, one would be led to a position of implicit atheism. This isn't the outright "denial" of a God, but rather the simple withholding of belief in such to render the claim and underlying entity redundant.

I'd like to outline the approach here, in terms of four overriding principles:

1) Ockham's Razor, which is the principle at the heart of scientific hypothesizing. That is, given two competing hypotheses, the one with the fewest ad hoc assumptions is closest to the truth.

2) The probability test of philosopher David Hume: "No testimony is sufficient to establish a miracle, unless the testimony be of such a kind that its falsehood would be more miraculous than the fact which it endeavors to establish."

3) The ignotum per ignotius test for logical fallacy. Ignotum per ignotius means [to explain] a thing not understood by one still less understood.

4) The fundamental principle for all exotic claims: "Extraordinary claims demand extraordinary evidence."

Let's now apply these principles to a number of cases to see how they work. I will start with the claim that humans have "souls." Given two hypotheses - one which uses simple observations of consciousness (as in Daniel Dennett's book, "Consciousness Explained") and one which posits "soul" in addition, which is to be preferred? Obviously, that which excludes "soul," since it unnecessarily complicates the issue. In addition, invoking "soul" violates the ignotium per ignotius test. Indeed, religionists have not even offered an operational definition for "soul." Until they do so, it is unlikely they can provide extraordinary evidence for it!

What about "God?" All the same aspects apply. Consider the question posed by the late astronomer Carl Sagan in the "Cosmos" episode, The Edge of Forever. He asks: "How did the universe begin?" He answers, "Some will say 'God made it', but then WHO made God?" He argues that rather than inviting an "infinite regress" of cause, the simplest action was simply to leave "God" out of the causal nexus. Thereby we satisfy all the principles (1) through (3).

Is Sagan's reasoning justified? Consider that adding "God" to the mix doesn't enhance cosmological data or predictions one iota. Nor does it refine the tensor equations. Clearly it amounts to a redundancy.

Lastly, consider the claim of a miracle, Jesus' walking on water. Professor Hugh Schonfeld has a simple explanation for this: a mistranslation of the Hebrew word "al" which can mean "by" or "on." So, when a scribe really wrote "walking by the water," it was translated to "walking on the water."

Now let us apply the Hume test (principle 2 above). Is the Schonfeld claim of mistranslation MORE or LESS miraculous than a man actually violating the law of gravity and walking on water? It doesn't require a lot of thought to see that the mistranslation of a passage of the New Testament is less miraculous (or if you prefer, less improbable) than a man actually, literally walking on water.

Understanding these principles, one can see how a basis for atheism is rational.