I was talking to a real religious guy who asked me “How do you know you’re not just in the imagination of some person strapped down in a psycho ward? Or part of the Matrix?” I said I didn’t know, and how did he know he wasn’t. He shot back
My religion makes me certain I’m leading a real life.
Hhhmmmmmm…Does religion prove the reality of existence?
Really? You’re going to bring that lame ass argument to GD and expect others to deal with it?
How does he know his god isn’t imagined by the guy strapped down in the psycho ward?
edited to add: “Certainty” and “Reality” have two different definitions in the dictionary for a reason.
What did he say when you asked him to prove it?
Go to your room! 
What would he say to a worshipper of a pagan deity, who patiently explains that she knows the truth about reality because of her wise and mighty goddess?
No. I don’t know the truth of reality, and I don’t worship any deities. I just try to live in the present, doing each day as best as I can, even if I’m only in the thoughts of a psycho.
I know I don’t know (as opposed to believing) the truth of reality. How does knowing God make reality real?
Did you ask the person who said it? if not, how are we supposed to know what he was thinking?
Just to clarify, I wasn’t trying to suggest you worship a goddess. I’m asking how he’d reply to someone who confidently asserts that they know they’re living in reality because they learned it from – a deity he doesn’t believe exists.
I figure he’d maybe react to her the way you’re reacting to him: sensibly. (Or, failing that, he’d say “nuh-uh, you’re wrong” to her, and she’d say “nuh-uh, you’re wrong” to him, and you’d ask for a tiebreaker…)
No, the reality of existence validates religion
Seriously. The antithesis of religion is a mechanical deterministic world in which everything, including “the illusion of consciousness”, is without meaning. That no purpose exists anywhere at any time, that instead of any forward-looking reason for anything there is only a backward-looking explanation in the form of prior causation.
Existence that has no meaning or purpose, of which there can be no understanding but only the illusion thereof, is not different from the absence of existence.
This is like asking us to tell you where your friend left her car keys.
I’m guessing he’s a fan of Descartes. His argument proving he and everything else was real is basically:
I’m thinking, so I know that I’m real.
Because God’s described as being perfect and one of the properties of perfection is existence, God must be real.
God isn’t evil and wouldn’t torment me by lying to me about the nature of reality.
Therefore everything I experience is real.
There are some obvious problems with Descarte’s reasoning that are not only a consequence of my simplification.
And that’s really the key point. People are frequently certain of things that aren’t true. Certainty has limited value.
:: coughs ::
The “we could just be a computer simulation/dream/characters in a book” argument has no rebuttal. It could very well be true and we’d never be sure. The thing to do is just live life like it’s real either way.
It’s a matter of faith, basically. Secular faith, but faith nonetheless. One of the basic axioms of a rational worldview is that an external reality exists, and that we can accurately learn about it through our senses and the tools we use to extend those senses. If that’s not true we basically have to throw out all of human knowledge and any potential for future knowledge.
A few things I have leaned right here on the dope have caused me to rethink my beliefs on existence.
The first one is that antimatter can annihilate matter and both will cease to exist.
The other one is that if we removed all the empty spaces that exist in matter only a very small super dense glob would remain. It makes me question my own reality.
From the conversation reported in the OP, the religious guy didn’t claim that his religion proved the reality of existence, but rather that his religion gives him subjective certainty about it. He’s therefore trying to show one of the meaningful benefits he derives from his beliefs, which even if the logic doesn’t follow is still demonstrable.
This is the most charitable interpretation I could manage.
Listen to the Bruggencate/Dillahunty debate to get a handle on how empty the “you can’t know you know, but* I *know because God” position really is.
And if every universe can host more than one simulated universe, the odds are infinitesimally small that we’re in a “real” universe.
As the song goes, “If you’re wondering how he eats and breathes / And other science facts / Then repeat to yourself ‘It’s just a show, / I should really just relax’.”
The argument is called solipsism and isn’t particularly helpful.
Once you reach the part of the argument where people starting saying things like “what if the whole universe is an atom in a giant’s toenail?” it’s time to say “fuck it dude, let’s go bowling.”
Unpacking his answer, it is just that - HIS answer. First, he seems to desire that he be leading a “real” (his definition) life. Next, he seems to desire that he have “certainty” about this. So, for him, religion provides the certainty.
Now, do you desire that you be leading a “real” life - in either your own, or his definition?
I don’t.
Do you desire certainty about this?
Again, I don’t.
Therefore, there is no need for religion (to provide the certainty.)
Your friend was attempting to create a rhetorical trap for you, so that he might feel superior, and “prove” that his way is THE WAY. A common mistake among the faithful.