Life, the Universe, and One Brow

With formal systems, such as mathematics, you can have certainty and demonstrability, but not reality.
With science, such as physics, you can have reality and demonstrability, but not certainty.
With belief systems, such as Christianity, you can have reality and certainty, but not demonstrability.

After the great example of St. Thomas, the principle stands, or ought always to have stood established; that we must either not argue with a man at all, or we must argue on his grounds and not ours. We may do other things instead of arguing, according to our views of what actions are morally permissible; but if we argue we must argue "On the reasons and statements of the philosophers themselves."

Any habitual action, such as eating or dressing, may be performed on the appropriate occasion, without any need of thought, and the same seems to be true of a painfully large proportion of our talk.