Question: “What exactly is written on the hearts of Gentiles in Romans 2? The entire Mosaic law or just part of it?”
Answer: The Gentiles (all unbelievers) have a standard of righteousness (alluded to in Jn.16.8ff) written on their hearts, which is the *functional equivalent* or “work” (“Do this and live!”) of the Moasic order.
v12 All […Gentiles] who have sinned [which is ALL Gentiles] without the law [of Moses] will also perish without the law [of Moses]
v13 …the doers of the law [Law of Conscience (Gentiles) & Law of Moses (Jews)] who will be justified.
v14 …Gentiles, who do not have the law, by nature do what the law requires, they are a LAW TO THEMSELVES, even though they do not have the law.
v15 They show that the WORK of the law is written on their hearts, while their CONSCIENCE also bears witness…
* More to come….