There's no quick answer here. Epistemology is an involved topic.

Looking at the birds and the trees, and other life forms out the window, are cited as evidence for a god. "The evidence is all around you!".

But we're not ignoring anything... instead, virtually no evidence is actually provided. Many people seem to think "evidence" is merely anything that's consistent with what you're saying. It's not. Atheists receive an earful of such arguments, and little by the way of actual evidence.

Put another way, what evidence for a god has been provided that...?

  • is repeatable/reproducable.
  • is logical (logically follows, and doesn't employ any logical fallacies (hint: "We don't know how else this could have happened" doesn't qualify)
  • is exclusionary (the evidence implicates a very narrow set of possibilities)
  • is objective (no "I had a vision" claims, sorry)
  • is presentable (no "I have the evidence, but I can't show it to you")
  • follows Occam's razor (accounting for the most data with the fewest assumptions)

Missing one of the above requirements invalidates the usefulness of the "evidence" in question. It's difficult to think of anything we've been presented that qualifies as evidence, let alone good evidence.

Yet, even if we had one good piece of evidence, that's not enough. You still need to have sufficient good evidence to build a solid convincing case, especially if it contradicts established science.

Imagine you're at a car dealership, and you ask why you can't purchase a particular car. The salesperson says, "Because you didn't bring any money". A reasonable person wouldn't think that giving $1 to the salesperson means the Corvette is now purchased. No, it costs $25,000. The salesperson just phrased the problem poorly.

Atheists make this same mistake frequently when asked "Why don't you believe in a god" and the atheist replies, "Because you haven't given any evidence."

Good versus bad evidence

For assessing the value and quality of asserted evidence, we have the Standards of Evidence. Some attributes make a piece of evidence more valuable than another piece.

Which is better evidence that a tornado occurred?

  • A candy bar with a face chiseled into it.
  • A path of destruction with objects strewn randomly left and right.

Obviously, the latter is the better evidence - but, why? When one starts analyzing what makes some evidence better than others, one would soon develop a set of rules, or a set of standards, of what makes for good evidence, or bad.

• As a general rule of thumb, if the evidence one is offering equally (if not more) implicates the opposing viewpoint, it isn't good evidence.

Pointing at the birds and the trees implicates, even more so, that nature happens, and operates on its own. It's a direct demonstration of a system that has no other engine driving it. This is exclusive with the claim that it does. We've never observed any "supernatural" phenomenon spontaneously creating new forms of life. We only observe nature operating, as nature usually does.

• If one is responsible for hiring good, hard-working and experienced people into job openings for a company, one typically has a set of standards established that are consistently demonstrably effective at weeding out bad candidates and finding the good ones. If a person applies for a job, and instead of supplying previous employers as her references, she instead provides references to her imaginary friends, and instead of a resume indicating experience, she has a resume that talks about hallucinations she had about doing work, that candidate would be promptly dismissed, and rightly so.

• Often, theists will attempt to "logic God into existence", without any attempt to confirm the argument. An example is, "God is love. Love exists, therefore, God exists." Simple logic is used without any confirming evidence, often on faulty or undemonstrated premises, to argue that a God must exist. Since logic can only be a guide for investigation in reality (you can only absolutely prove things within math), all one has done is made an argument without any verification.

• The vast majority of theistic arguments fail for one reason or another, to the point that it's rare to hear an argument that doesn't use at least one logical fallacy.

That's why most "evidence" provided by theists gets rejected; because the quality is too poor, invokes common logical fallacies, and doesn't adhere to basic standards of evidence.