Rom.2:14,15 – Even Gentiles, who do not have God’s written law, show that they know his law when they instinctively obey it, even without having heard it. They demonstrate that God’s law is written in their hearts, for their own conscience and thoughts either accuse them or tell them they are doing right.
According to this verse Paul believed and taught that all mankind, Jews and gentiles alike, had something of God’s law in our hearts. Even after the fall there remains in all of us something of God’s moral code written within us. Because of our fallen nature we don’t have the capacity to follow our conscience, nevertheless it remains a constant reminder that we were created in the image of God. This is why humans from all ages have tried to create a religious system based on their version of the moral code written inside of all of us. From Buddhism to Islam, humans have created intricate systems of some sort of law based on this inner moral code. Sadly, no religion has the power to enable us to overcome our fallen nature. Only the gospel that provides a new heart within all that believe has the capacity to live this life that we all long to attain to. Here is how Albert Barnes describes this law written in our heart.
“The revealed Law of God was written on tables of stone, and then recorded in the books of the Old Testament. This law the Gentiles did not possess, but, to a certain extent, the same requirements were written on their hearts. Though not revealed to them as to the Jews, yet they had obtained the knowledge of them by the tight of nature. The word ” hearts” here denotes the mind itself, as it does also frequently in the Sacred Scriptures; not the heart, as the seat of the affections. It does not mean that they loved or even approved of the Law, but that they had knowledge of it; and that that knowledge was deeply engraved on their minds.”
The changed heart shows the superiority of Christianity over Judaism as well as all other religions or religious codes. Our nature is dramatically changed by the new birth, in Christ we can finally begin to live the way we know we should. Paul shows that all of us are sinners in need of a Savior. Only Christ has they ability not only to forgive us but dramatically change who we are.