First, there's this video - you need to fast forward to 7 minutes, 45 seconds to get to the good stuff:
His response *seems* logical, but there's a big flaw.
The lady at the beginning: "I refute your argument that logic could not have been created by minds because they are different, then use that argument to claim that god exists. Logic has resulted from thinking, through the ages...."
Now, Rev Slick's argument (after diverging into the "atheists can't tell good or bad through logic," which is another fail whale of epic magnitudes we won't address here) goes like this:
1. All information comes into the brain
2. The brain forms results through neurons firing
3. Everyone's brain can't actually interact with the information, but with the information from nerves in the body - they aren't touching *direct* information, but interpreted information
4. Because you're not experiencing true objective reality, but a subjective one, you can't say whether someone else's perspective on reality is true or false
5. Because of this, minds can't create logic. Therefore, logic must come from somewhere else - which is God.
Now, I would have agreed with him up until Point 4, and then it makes that huge "watch while I dazzle you with magic!" bullshit argument.
It's true - what's inside your brain may be different from what's going on inside my brain. But that doesn't mean that just because things are different and we're not experiencing "objective" reality that we can't agree.
Suppose there's a wall in front of me. If you're an insane person, you keep bumping into the wall and say "I've just run 100 meters!" Me, as another observer, can say "Well, I don't know what's going on inside your head, but no matter how much you claim otherwise, you haven't gone more than 1 meter because you keep bouncing off this wall." Two different people, two different observations - but in the end, there is only one objective reality.
And how do we measure that objective reality when we clearly have different opinions? We both create our experiments (If you can really go 1000 meters, you should be able to get this glass of water. If not, then my hypothesis that you're running into a brick wall is correct.) We can set up the experiment, invite others to join. Sure, there may be other insane people out there, but the trend will be that far more people will reach my conclusion from the experiment than not.
The insane person may have *faith* that there is no wall there, and others may believe it, and they may even believe that they're drinking the water from the glass 500 meters on the other side of the wall. But, I'm willing to bet, 99% of the people who repeat my experiment will show "Yeah, that wall keeps blocking off his access. That dude is in*sane*."
Wait - we've just come up with a way of validating objective reality, and we can call it the scientific method. Yay! So now we have a way of establishing, via a logical system of evidence gathering, whether there is a "true" reality or not. Sure, it may take some time, but it would work.
Granted, evolution has done much of that for us. People who think they're really drinking water when they're not tended to die out, so our complex brains have evolved lots of shortcuts to judging reality - and in a way that most people would agree with - so we don't have to go through this scientific process over and over again.
"But wait," our faith based insane person says, "That may explain objective reality, but you haven't explained good and evil! How can you decide whether something is good only through logic!"
The first problem is that this is a falsehood in the question - you can't establish morality from pure logic alone. That would be like doing math to decide whether "I Wish That I Had Jesse's Girl" is the greatest song ever (which it is).
But, we can use that old "let's start with some premises and go from there." I hold out the premise that I do not want to be murdered. I enjoy breathing, so I'd prefer *not* to be bashed upon the head until I no longer breathed.
I believe I can assume that *you* don't want to be murdered, since (sharing an objective reality), likely you have the same feelings and emotions and survival drives as I do.
We now have established a shared morality: being murdered is the suxxors, so let's agree not to murder each other. But, because there may be irrational people who have faith that murder is A-OK, let's set up a system where we all agree not to murder each other, and those who don't want to participate in this system get kicked out of town - let the pro-murder people live outside. Maybe hold an election and see who we want to enforce the law of "murder - is bad for you" and patrol people to keep the pro-murder forces out. If someone does murder someone in the town, then that person will be punished (or if possible, reformed so they know that murder is bad, m'key?).
Now, again, evolution did a lot of that for us (those who ran around killing their local human beings tended to get offed by the other human beings so they couldn't reproduce. Sure, history is full of us slowly moving from cavemen who thought that was a great way of settling disputes, but over time we eliminated not all, but a lot of those genes. Sadly, too many of them were carried into chicken hawks who like to never be in the military but love them some war. I'm digressing now.).
Either way, Rev Slick's assertion that "logic can't explain good or evil because we can't get an objective reality because our brains are all subjective so God did it" is pretty quickly taken apart once you realize that yes, we *can* reach some *approximation* of reality through our senses and a system (which evolution mostly did the heavy lifting for, so we don't argue whether the car is gray or red - unless damaged, we both agree that the car is gray because it's my awesome gray Beetle and no you can't drive it). And, while logic alone - no more than math alone - could deduce morals (and reality, not its job), we can *use* those tools (created by human minds, by the way, to explain the reality around us) to deduce morality based on a few core principles and extrapolating from there.
I think I'm gong to get a lot of TL;DR, aren't I?