Charles Ellicott Commentary Romans 2:15

"in that they show the work of the law written in their hearts, their conscience bearing witness therewith, and their thoughts one with another accusing or else excusing [them]);" — Romans 2:15 (ASV)

Which.—Rather, Inasmuch as they.

The work of the law.—The practical effect or realization of the law—written in their hearts as the original Law was written upon the tables of stone (2 Corinthians 3:3).

Also bearing witness.—Or, witnessing with them, as noted in the margin. There is a double witness: their actions speak for them externally, and conscience speaks for them internally.

Meanwhile.—Rather, literally, as noted in the margin, between themselves—that is, with mutual interchange, the thoughts of the heart or different motions of conscience sometimes taking the part of advocate, sometimes of accuser.

This seems, on the whole, the best way of interpreting these two words, though some commentators (including Meyer) regard this quasi-personification of “the thoughts” as too strong a figure of speech, and interpret “between themselves” as referring to the mutual interaction of human beings. But in that mutual interaction it is not the thoughts that accuse or defend, but the tongue. The Apostle is speaking strictly of the private tribunal of conscience.