I was reading the book Angels and Demons by Peter Kreeft awhile back, and he mentioned something about how we are the only creatures created by God who are both spirit and body. Angels have no body, and animals (excluding humans) have no soul. We are the only beings we know of who have both.
We can't see angels because they have no bodies. We can't touch them, hear them, smell them, (taste them), because doing all these things would require them to have physical properties. Kind of like our thoughts really. You can't see, hear, smell taste or touch a thought, but you know it is there. In fact, the more I think about the way Peter Kreeft describes angels, the more I think angels are just that. Thoughts personified. They move by thought, they are with you by thought, they only have to think of a place or a person to be there. They can be thinking of more than one thing at once and concentrating on more than one thing at once, so they can be in more than one place at once. Our guardian angels are always in contact with both us and God for example. Think of it like telekenisis. They have no bodies, therefore they do everything by mind. So if angels can control things by telekenisis, it would be only logical to assume that the accounts of some humans being able to do the same as well, might not be so false, if they were able to control that part of their spirits. Much of our brain goes unused, apparently. Perhaps it is not illogical to assume that we might be capable of certain things, if we knew how to use it properly.
Since God is also a Spirit, He works in much the same way, only he is much, much more powerful. And the second person of God is also fully human. Which is really amazing.
So how do I know that God really does exist and that God and angels aren't just some kind of silly hocus-pocus, the the religious right would have us believe in order to keep us in the so-called Dark Ages?
Because I have a soul. Because I have fed that soul, developed it, prayed with it. Why do we have a soul? So that we could know God. We couldn't know God if we didn't have a soul. How could something purely physical ever know something purely spiritual? (Not even when Jesus spent 33 years here, would a purely physical being have recognized him for anything else but a physical being.)
I believe in God because my soul knows He exists. You cannot have had a relationship with a being and then doubt his existance. The more I pray, the more I know God exists. The more time I spend in His presence, in communion with Him, the more I know He exists. I cannot prove it physically, but I know it spiritually.
To know God exists, you must pray. You will never know he exists if you choose to ignore that part of you. Praying is not just asking for things, like that little red wagon you always wanted, and then giving up on God because it wasn't there under the Christmas Tree. God doesn't always give you what you want. (Sometimes he gives that job to your parents) But He'll always be there for you, and you'll know this if you're willing to listen to what HE has to say as well.
God has spoken to me through my friends and family and of course, through the Bible. Sometimes, a thought comes into my head, that seems to be an answer to a question I have been trying to deal with, and from the way that thought comes and the timing of it, I know God has put it there.
God exists. He really does. But it's no use reaching out to Him in physical ways (well, excepting the sacraments of course, which he has given us, obviously because we are physical beings and need physical signs), you have to reach out to God with your soul. That is the only way to find Him, to know Him.