Augustine of Hippo

If they are not seen, how can you be convinced that they exist? Well, where do these things that you see come from, if not from one whom you cannot see? Yes, of course you see something in order to believe something, and from what you can see to believe what you cannot see. Please do not be ungrateful to the one who made you able to see; this is why you are able to believe what you are not yet able to see. God gave you eyes in your head, reason in your heart. Arouse the reason in your heart, get the inner inhabitant behind your inner eyes on his feet, let him take to his windows, let him inspect God's creation.