You don’t have to “know” a rule to know that you should be following it. Take, for example, the rule of ablaut reduplication. Chances are, you have never heard of it, but you follow it all the same. Writer Mark Forsyth explains in his book Elements of Eloquence:

There are rules that everybody obeys without noticing … Have you ever heard that patter-pitter of tiny feet? Or the dong-ding of a bell? Or hop-hip music? That’s because, when you repeat a word with a different vowel, the order is always I A O. So politicians may flip-flop, but they can never flop-flip. It’s tit-for-tat, never tat-for-tit … If you do things any other way, they sound very, very odd indeed.

Teachers do not have to teach this rule in grammar school. But it is known all the same. Even when we don’t officially know the rules, we instinctively know we should follow them and can immediately identify when something is wrong.

Possible Preaching Angle: Conscience; Morals; Law of God – The same is true spiritually for each person on earth. God has “written the requirements of the law on their hearts, their consciences also bearing witness” (Rom. 2:15). Though people try to ignore it or silence it, each one has a conscience that speaks of God’s rules.

Mark Forsyth, “The Elements of Eloquence,” (Berkley, 2014), Page 46