After almost a dozen years of writing Church of the Churchless posts, and reading comments on them, I'm familiar with the arguments religious people use to justify their beliefs.
When I point out that there is no demonstrable evidence supporting a belief in God, heaven, soul, spirit, angels, the afterlife, or any other form of supernaturalism, frequently I'll hear something like this:
Hey, Brian, you can't prove God doesn't exist, so there's no proof for your skeptical view either. Thus, it's a tie! There's no proof God exists, and there's no proof God doesn't exist, so it's up to each person to decide which "no proof" to accept.
Well, typically I respond by saying that the way both science and common sense works is that we believe in the existence of something when there is good affirmative reasons to say "it exists."
If we demanded proof that something doesn't exist before giving up a belief in it, there would be no end to the absurd views of reality that would result. Such as...
"Fairies make the flowers in gardens grow. I know this because you can't prove fairies don't exist."
Today I was reading a book I bought recently, "Human Universe" by physicist Brian Cox (it is based on a BBC program). Here's a passage that nicely presents the scientific point of view that I share, but can't express as well as Cox and Richard Feynman did.
Brian Cox writes:
I'll put my cards on the table here. I believe in UFOs. That is to say, I believe that there have been sightings of flying things in the sky that the observers were unable to identify, some of which were objects.
But I do not believe for a moment that these were spacecraft flown by aliens. Occam's razor is an important tool in science. It shouldn't be oversold; nature can be complex and bizarre. But as a rule of thumb, it is most sensible to adopt the simplest explanation for an observation until the evidence overwhelms it.
My favourite response to the criticism that dismissing the possibility of alien visitations to Earth is unscientific was provided by physicist and Nobel Laureate Richard Feynman in his Messsenger Lectures at Cornell University in 1964:
'Some years ago I had a conversation with a layman about flying saucers -- because I am scientific I know all about flying saucers! I said "I don't think there are flying saucers". So my antagonist said, "Is it impossible that there are flying saucers? Can you prove that it's impossible?"
"No, I said, "I can't prove it's impossible. It's just very unlikely." At that he said, "You are very unscientific. If you can't prove it impossible then how can you say that it's unlikely?"
But that is the way that is scientific. It is scientific only to say what is more likely and what less likely, and not to be proving all the time the possible and impossible.
To define what I mean, I might have said to him, "Listen, I mean that from my knowledge of the world that I see around me, I think that it is much more likely that the reports of flying saucers are the results of the known irrational characteristics of terrestrial intelligence than of the unknown rational efforts of extraterrestrial intelligence."
It is just more likely. That is all.'