In my previous post I talked a bit about the high standards of evidence that skeptics demand before believing in something. A bit more on that subject:
As I said in the previous post, evidence is valid only if it passes the rigorous test of science and peer reviewing. However, there's still another aspect of this that also has to be considered: Just because the evidence has been verified as valid, that still doesn't actually tell us what it's evidence of. We should always be cautious to avoid jumping to conclusions even if evidence turns out to be completely valid. The next big question should be: "What exactly is this evidence of? What's actually the cause behind it?"
Let's take an example: There's undeniable, verifiable and repeatable evidence that stars in galaxies rotate at orbital velocities that do not match the apparent mass of those galaxies. Normally the orbital velocity of a star should diminish the farther away it's from the center of the galaxy, so that stars far from the center move at a much slower velocity than stars close to the center. However, the orbital velocity of stars in galaxies is almost the same for most of them.
This is scientifically valid evidence. It can be observed and measured, and these tests can be repeated over and over by independent, unbiased parties. Thus there's no doubt that the phenomenon exists.
However, the big question is: What causes this? Scientists do not jump to conclusions. Hypotheses are presented, but until those hypotheses can be verified with actual observation, measurements and testing, they are not accepted as valid.
In other fields many believers in the supernatural, conspiracy theories, etc. succumb to a kind of circular reasoning. When faced with evidence that seems valid, they will offer a cause or explanation for it, even though it might not be warranted. When asked to justify the claim, they will present that evidence itself to justify it. This is just circular reasoning.
To understand what I mean, assume that someone said "the orbital velocities of stars in galaxies is caused by unseen dark matter". Then someone asks: "How do you know?" That someone says back: "Well, you can measure the speed of stars in galaxies. They have all the same orbital velocity."
You see how this doesn't work? If you present an explanation for observed evidence, and then back up your claim with the very same evidence, you are not getting anywhere. It's a circular argument. The evidence shows that the phenomenon happens, not why it happens. It's the same as "God created life." "How do you know?" "Well, life exists, doesn't it? There you go, undeniable evidence."
Or like in a Monty Python sketch: "What are you doing to that woman?" "We are going to hang her because she's a witch." "How do you know she's a witch?" "Well, we wouldn't be hanging her if she weren't, now would we?"
However, that's exactly what the believers and conspiracy theorists do. And they don't even realize it.