A frequent example of fallacious thinking lies in the phrase "there is no evidence either way." There is either no evidence to support a proposition or evidence to support a proposition; there is no such thing as "no evidence either way." If evidence is inconclusive or a stance can not be taken, agnosticism, in the true sense of the word (not enough knowledge to make a decision), is a tenable stance, but this is much different than "no evidence either way."
The category of "no evidence either way" is the same as "no evidence." Is there "no evidence either way" to support the existence of Bigfoot or the Loch Ness Monster or is there simply no evidence? Is there "no evidence either way" to support the idea that King Arthur existed or is there no evidence? Is there "no evidence either way" to suggest that the moon landing was faked or is there no evidence to support this idea?
"No evidence either way" frequently pops up as a last ditch argument for the theism, but theists ought not say this because it contradicts their own position (they believe in a god). Of course not all theists use this phrase, but some unfortunately do.
Imagine that I said "There is a ten dollar bill in my pocket" and you had no idea about the contents of my pocket. If I would ask you to decide whether there is or is not a ten dollar bill in my pocket, you should say something along the lines of, "I don't know. I don't have any reason to suggest that there is or is not. I need more information." It would be odd and incorrect to suggest that there is no evidence either way; you simply have no reason to suggest that there is a ten dollar bill in my pocket.
Might the ten dollar bill be in my pocket? Sure, there might be a ten dollar bill, but with your current information, you should withhold belief and/or not believe that there is a ten dollar bill until you see good reason to suggest that there is a ten dollar bill in my pocket. If I never allow you to inspect my pocket, you should never say "there is no evidence either way," but rather should say, "I have no reason to suggest that there is a ten dollar bill."
Now, let's return to theism. The position of the theist who says that "there is no evidence either way" is laughable. If we even allow for this third category of "no evidence either way" and a person takes this position, this person should be a non-believer because he/she has no good reason (by admission) to believe. If I took the position of solipsism (that everything is just a figment of my imagination) and I said that there is no evidence either way to suggest that everything is a figment of my imagination, I'm clearly yielding my position.
Another fundamental fallacy in the phrase "no evidence either way" is that something can be "disproven." It's impossible to "disprove" something, but if we find no evidence to support a proposition, we should withhold belief/not believe rather than believing it. If a person is making a positive claim about something, the burden of proof is on him/her to demonstrate this. If I were to walk up to someone and say, "I could shoot lasers at streetlights by using my mind" and I failed to do so, it would be silly for the person to say, "Well, I guess there's no evidence either way to suggest that he can do what he says he could do."
If a person feels that there is no evidence to support the existence of God and no evidence to counter the claims made by believers, the person simply shouldn't believe. In what other area of life would we say "there is no evidence either way" and still believe in a specific claim? Let's not use glib phrases and make excuses when we have no evidence to support claims.
This wonderful video inspired this post and will recap my arguments: