Now, I'm sure many of you realized that 'Inception' is about religion, but I haven't noticed too many people talking about it so I will...
You're waiting for a train. Well, you're dying. A train that will take you far away. You know where you hope this train will take you. You want to go to heaven. But you can't be sure. But it doesn't matter - because we'll be together. Faith.
'Inception' is not about whether or not your world is real. None of Nolan's film are actually about that. 'Memento' doesn't say that you don't know if your memories are truth; it says that you lie to yourself to feel better. 'The Prestige' uses ignorance to show how feuds are one-sided and lack perspective. And 'Inception' doesn't say that the world around you is a lie. That has no real connection to us. It's really about how the world is a fight between faith, or believing, versus the unobtainable truth.
Dreams feel real while we're in them. We know what we know because what we know is what we believe. Mal 'knows' that she's in a dream because she believes she's in a dream. And these beliefs are unchallengeable. Nothing Cobb does can make her change her mind and realize the truth. Just like how, despite the amount of evidence against almost every religion in the world, people still believe. Mal tries to justify her belief without any proof, while proof mounts AGAINST her case. Nothing can change her mind. Faith is a dangerous, undebatable thing.
But Nolan also points out the good in faith, which I think is the point and center of the entire film. The truth sucks. And Cobb realizes this. He's constantly torturing himself with the possibility that everything around him is a lie, which is why he's constantly spinning his top. But that's horrible. And he realizes this. His projection of Mal (Cobb's subconscious) is constantly ordering him to ignore reality and embrace faith. You keep telling yourself what you know. But what do you believe? And faith, as dangerous as it is, can make life better. The 'Waiting for a Train' quote represents our fear of the unknown. When we die, what will happen? We don't want to stress over the possibility that when we die we experience nothingness in a wooden box of eternity. We want to go to a better place, far from here, where we'll meet up with everyone we've lost. We want a heaven. Heaven is the train we hope to take, that we believe we'll take, because that makes death a little less terrifying. 'Waiting for a Train' is Nolan's analogy for heaven.
Now, I'm not discussing whether the end of the film was real or a dream. That doesn't matter. What matters is that Cobb doesn't care. He spins his top, sees his children, and leaves the top spinning. He doesn't know if it falls or spins forever. Why would he? To him, this is what is real. He doesn't want the truth because the truth can be something awful. He could be in a dream, but why would it bother him if he doesn't know that? He can continue his life in the dream if his faith tells him that his children are real and that he is awake. Sure, the top could fall over, but the possibility of him being in a dream remains. We choose to believe what makes us happy.
What's genius about the final few seconds of the film is not that it makes you question your own reality. It's that it proves Nolan right. Raise your hand if you have a belief that the film is real or a dream and if you will argue your belief to the death. You don't actually know the truth behind the ending. No one does. But you think you do. Your faith says you're right.
And I could go on and on about how genius Nolan's themes of idea and influence are but I'm tired.
So, there you have it. 'Inception' isn't about reality, it's about faith and religion. And I've probably just told you all what you already know...sigh...
), but I think that religion was the point Nolan was trying to get across in this film. 
