Religion.

How can you say I can't believe in something I've never seen?
I can't see your brain, so I suppose that means you don't have one.
Look around you, admire the things that you see outdoors. Examine the bark on the tree & smell the flowers scent. Watch how the birds fly, see how they soar freely through the air.  You can't tell me that they just appeared there for no reason. You can't just tell me it's all man made, that someone picked something up and decided that it was going to be able to cut through the wind and soar on a wing of feathers. You can't just tell me someone just combined a bunch of scents and put them together in the ground and tended them to make them come out like that. You can't tell me that it wasn't God who created such wonderful things. 
Air and wind. You can't see it, but you know it's there, You've felt it caress your body on a hot day. You can't see it, but you can feel it and see how it works. It's how I feel about God. 
I believe in him because I've felt his presence. I've felt him feel disappointed in me. I've felt him smile and feel proud of me, I've felt him be there for me when no one else was. 
I've felt it. & You haven't.
 Yes, I do believe in something I can't see, but you're the one I feel sorry for.