When it comes to the material world, it is easy to prove the existence of something that can be seen, felt, or smelled. All you have to do is show a person that thing, and its existence is "proven."
On the other hand, immaterial things are much more difficult to "prove" from a sensory standpoint. You cannot point in a certain direction and show someone their Guardian Angel.
Angels by their nature do not have a physical body and so exist in a realm that is invisible to our senses. No matter how hard I try, I'll never be able to squint my eyes enough to see the spiritual being that was assigned to be my guardian.
So how can I prove their existence, if I can't see them?
If God exists, then why not angels?
The entire question regarding the existence of angels hinges on the existence of a spiritual being we call God.
Peter Kreeft spends an entire chapter exploring this concept in his book, Angels (and Demons), explaining why it makes rational sense that angels exist:
If you can prove the existence of the supernatural, then there is a "place" for angels, a category for them to inhabit. If there is a God, why not angels? If there is an infinite spirit, why can't there be finite spirits?
In many ways the supernatural is impossible to prove through a person's senses, but at the same time, it is also impossible to prove that the supernatural does not exist.
In a similar line of reasoning Kreeft writes, "How could an unborn baby prove there is no life outside the womb? How could man, bound to nature, prove there is nothing in addition to nature?"
Kreeft then points to C.S. Lewis' book Miracles as a good starting place for anyone questioning the existence of the supernatural. Lewis explains in his book why it is rational that there would be something beyond our human senses.
If God exists, then the line of questioning would eventually end in the question, "Which religion is the true religion?" Then once that is figured out, the existence of angels is based on the teachings of that religion.
In the Catholic Church, we have a firm belief in angels, as the Catechism of the Catholic Church explains, "From its beginning until death, human life is surrounded by their watchful care and intercession" (CCC 336).
While we may not be able to see our Guardian Angel, the limitation of our senses does not negate the reality of a whole spiritual realm that lives on an entirely different plane of existence.
