By far the best proof is experience.
God loveth the clean.
Liberty of speech invites and provokes liberty to be used again, and so bringeth much to a man's knowledge.
It is a great happiness when men's professions and their inclinations accord.
Small amounts of philosophy lead to atheism, but larger amounts bring us back to God.
For it is most true that a natural and secret hatred and aversation towards society in any man, hath somewhat of the savage beast.