I remember a conversation I had discussion about angels which I said might be seen as forces, unseen by most of us but real. Two listeners thought I was nuts, of course, and then I held up my cell phone. But you take this unseen "force" for granted. Do you see the force that sends these messages? No answer. It at least made them think. The world around us that is invisible to most of us, could some "see" it but not through the five senses necessarily. Think of what dogs can hear and what bats can detect.