When the Gentiles do things like pay their debts, honor their parents, show
kindness to the poor, condemn murder, etc., they are doing what the Mosaic Law commands - even though they have
never
heard the
Mosaic Law!
Paul tells us that when the Gentiles naturally do the things that the Law requires, they show
that they have a law in themselves (written on their hearts). That is, they have
as a part of their nature a sense of duty, a sense of right and wrong - apart from any external law.
Paul tells us that the Gentiles conscience works in their inner thoughts as a judge of
their behavior - on
some occasions accusing them (of wrong behavior) and other times defending them (for having acted in a manner that they
believe to be right).
Note
Paul is not saying:
That the Gentiles have the entire Mosaic Law written on their hearts - they have a law written on their hearts
giving them a general sense of right and wrong which (sometimes) results in
their meeting the requirements of the Mosaic Law.
That the Gentiles are infallible in their sense of what is right and wrong - only that they (sometimes) do (some
of) the things that the Mosaic Law requires.
That the Gentiles kept the law on their heart perfectly - as Paul has shown in Romans 1:18-32 (and in
Although they know God's righteous decree that those who do
such things deserve
death, they . . . continue to do these very things. (Romans 1:32)
. . . their thoughts now accusing . . . them. (Romans 2:15)