Of all the heresies I might have fallen into if it weren’t for the Magesterium of the Church, I’ve often thought that Gnosticism would be at the top of the list. I naturally have little use for the physical world. I try to move as little as possible, and would be content to just sit motionless and do intellectual or spiritual exercises all day (I once saw a science fiction movie about a man who was nothing more than a brain kept alive in a jar, and my gut reaction was, “Not a bad life!”) So the idea that the material world is useless and maybe even a little evil is an easy sell for me.
Especially once I came to believe in God, it sounded reasonable enough to say that the spiritual world is all that matters, that we can completely disregard all non-spiritual realities. After all, it is our souls that are of the realm of God! It is the spiritual realm that is our final and true home!
But then we have this little part of the Our Father, where we specify that our requests are to take place on earth. The Lord’s Prayer is incredibly efficient in its use of words, so it’s interesting that Jesus takes the time to add the “on earth as it is in heaven” part. Wouldn’t it be sufficient to say, “Thy kingdom come, thy will be done” and leave it at that?
When I meditate on this word “on,” it reminds me of the truth, counterintuitive to people like me, that the material world is not to be disregarded or disdained. God is an incarnational God. The second person of the Blessed Trinity became flesh, and walked on the earth. The Sacraments use elements of the material world as conduits of grace. Our souls are of God, but they are also inextricably entwined with the material world. On the Last Day our bodies, that part of us tied to the material world, will be resurrected.
So yes, we humans are spiritual creatures, part of the divine drama of the spiritual realm. But it is a drama that takes place in the material world, on earth.