I think that those who contend that "the law" was for the beginning are really referring to this. What I call God's law of human conscience. I resisted the idea of it being an authority, as you had said earlier, but am now coming around on that point.
I differentiate this law of human conscience from "the law" which God gave to the Israelites alone through Moses. Even though they are very similar in some respects. But if you don't make a point of separating them, people will think we are to keep the Sabbath and observe dietary laws, etc.
Romans 2:14-15
(Indeed, when Gentiles, who do not have the law, do by nature things required by the law, they are a law for themselves, even though they do not have the law. 15 They show that the requirements of the law are written on their hearts, their consciences also bearing witness, and their thoughts sometimes accusing them and at other times even defending them.)
Yes, you've nicely connected the dots. Our basic sense of right and wrong, and at minimum a primordial awareness of God's existence - what theologians call 'General Revelation' (Romans 1:18-20) is stamped into our souls by God. I suspect the human brain is largely part of His mechanism for creating the stamp, although that's another discussion. But yes, I think Paul formally refers to the stamp as the conscience at Rom 2:15.
How does it actually WORK? Feelings of certainty. To say that I feel certain whether an action is right or wrong is to say that I feel a sense of moral obligation, as an experience unknown to mere animals.
Left alone, however, conscience isn't well informed, for example it won't necessarily recognize the Incarnate Christ as the Messiah. So in addition to General Revelation we need Special Revelation. (In my opinion, anyone who acquiesces to the indistinctly-portrayed God of general revelation is rewarded with some degree of Special Revelation).
Special Revelation refers to the Holy Spirit directly influencing the human heart, persuading the conscience of something, via feelings of certainty, as a way of conveying information more specific, typically more accurate, than General Revelation. That's how we got saved. When this revelation is PARTICULARLY loud and clear - to the extent of persuading us to the degree of 100% certainty, I would classify it as PROPHETIC revelation. Only then is a person fully warranted in alleging, without disclaimers, 'Thus saith the LORD'.
That's why conscience is so relevant to the charismatic debate. The Inward Witness common to all Christians, is not distinct in KIND from prophetic revelation, it is only different in MAGNITUDE. The difference is quantitative, not qualitative. The same Greek word for 'reveal' and 'revelation' is applied both to prophets and to all believers, a fact conveniently glossed over in the writings of cessationists.
Many cessationists are hypocritical on this point. Meaning, they DO pray to God for insight and understanding, while repudiating prophecy! Essentially their daily petition is this, 'Dear Lord, please illuminate me today. But by ALL MEANS, do not speak to me as loud and clear as you did to the prophets!'
Sorry, but that attitude makes zero sense. That's total insanity. The church is founded on Special Revelation, and therefore the FULLNESS of Special Revelation should be a primary goal (1Cor 14:1). Interesting, isn't it, that Paul petitions God to grant the churches the FULLNESS of wisdom and revelation - i.e. he wanted them to reach HIS OWN LEVEL of special revelation. He never qualifies those petitions with the restraint, 'Except don't give them as much revelation as we prophets have enjoyed'.
I'm really spending too much time on this thread...