In a previous post on creationism, I used the word "concrete" when discussing the predictivity of scientific theories. What did I mean by that?
I gave one example of what a non-concrete prediction might look like. Many cranks have a habit of claiming that, since the dogmatic scientific community will be horribly undermined by their work, they're guaranteed to be laughed at. This prediction usually turns out to be true, which the crank claims supports a model of the world in which their notion is accurate and science is dogmatic.
Of course, the obvious response to this particular case is the infamous Carl Sagan quote: "They laughed at Columbus, they laughed at Fulton, they laughed at the Wright Brothers. But they also laughed at Bozo the Clown." However, there are some non-concrete claims that are less immediately laughable.
For example, many people present a variety of equally non-concrete evidences for God - a baby's smile, a sunset, a soaring bird. How, it's asked, can we see these things and not believe?
There are actually two answers to this. The more mundane one is that all this represents a rather impressive example of confirmation bias, the tendency to only remember half the story (in this case the good half). Incidentally, this form of bias is also the primary factor behind Murphy's law - it seems like toast always drops butter-side-down because, when it lands nicely, we don't feel annoyed enough to remember about it.
So, for example, the soaring bird is beautiful - but its subsequent evisceration by an unexpected hawk is less so. The baby's smile is lovely - but the other end of the baby is decidedly less pleasant. Sunsets can be gorgeous - until we recall that their vibrant colours are largely due to air pollution.
The second, more philosophically interesting, point is: it's not the baby, the sunset, the bird that's actually being offered as evidence. There is no logical progression from "baby smiles exist" to "God exists". What's really being presented as evidence is the intuitive beliefs that beauty exists and that beauty implies God.
Why can't we just accept that as scientifically useful? Because we have a long history of discovering that intuitive notions are wrong. The sky is not a big blue wall with holes in for rain and starlight. The Sun is not a small whizzy ball that spins round the Earth. Solid objects are actually probabilistic wavefunctions. Heck, space isn't even Euclidean. And yet, at various points in history, people have been sure of each of these to the point that expressing the opposite view would earn you a trip to the nuthouse*.
Given this repeated history of failure of "gut feel", why should the argument suddenly have far more credibility just because it's got the word "God" in it?
Disclaimer: as always, none of this means that God can't be considered real for an individual, or even real for the human species as a whole. It just means that the concept, as usually stated, doesn't necessarily meet the criteria to be considered real for any intelligent lifeform.
* In the case of the last two items on the list, these nuthouses still exist - they're called "universities"...