dear Tammy...
I believe the comparison is between jewish BELIEVING hearts and gentile BELIEVING hearts...
you seem to suggest that God writes SOME of the law on SOME non-believing hearts that aren't "stony" ...but you have to understand that the spirit of the written law didn't just include justice and mercy(characteristics some non-believers do display)...it contained the certain unquestioning seperation of the people from the surrounding nations for holiness to God...they were chosen by God tobe seperated under the law from everyone else.
that seperated "holiness to God" isn't written on the non-believers heart, at all, is it?...so thelaw isn't written on non-believers hearts...but it IS written in its entirety on a gentile believers heart. ie. seperated holiness to God, justice and mercy...because the spirit of the law IS kept by the same Spirit as Jesus Christ, Who fulfilled that law (but didn't do away with it).
Scripture says that no one is justified by works of the law but by faith in God and Jesus Christ. Without faith in God it is impossible to please God. That is the impetus behind preaching the gospel of salvation in Jesus Christ. There are the saved and the lost...not the saved AND the saved by their own works apart from faith in God AND the lost. (though you seem to believe that you've found a "loop hole" in the book of revelation that completely skirts the issue of salvation IN Jesus Christ alone)
That is why I suggest to you that the passage in matthew speaking about the sheep and the goats is talking about believers(warning them)...because though they had the law written on their hearts (both groups called Jesus Lord) both groups didn't fulfill the spirit of the law; that indwelling Spirit would have been urging them to "minister" to the needs of these people...just like Jesus did but, only the sheep who were led by that Spirit responded. The goats, though they professed Jesus as Lord, didn't allow themselves to be led by that Spirit...they had a "mind of their own"...like a stubborn goat. In this scripture there is agreement with what Jesus said about some who thought they were saved but are told to get away...Jesus never knew them.
The bible itself is a tool inspired for ministry of the gospel, it isn't a tool to reassure non-believers they can be saved by good works.
love michelle