Romans 2:15

In that they

(οιτινες). "The very ones who," qualitative relative.Written in their hearts

(γραπτον εν ταις καρδιαις αυτων). Verbal adjective of γραφω, to write. When their conduct corresponds on any point with the Mosaic law they practise the unwritten law in their hearts.Their conscience bearing witness therewith

(συνμαρτυρουσης αυτων της συνειδησεως). On conscience (συνειδησις) see on 1 Corinthians 8:7; 1 Corinthians 10:25; 2 Corinthians 1:12. Genitive absolute here with present active participle συνμαρτυρουσης as in Romans 9:1. The word συνειδησις means co-knowledge by the side of the original consciousness of the act. This second knowledge is personified as confronting the first (Sanday and Headlam). The Stoics used the word a great deal and Paul has it twenty times. It is not in the O.T., but first in this sense in Wisdom 17:10. All men have this faculty of passing judgment on their actions. It can be over-scrupulous (1 Corinthians 10:25) or "seared" by abuse (1 Timothy 4:12). It acts according to the light it has.Their thoughts one with another accusing or also excusing them

(μεταξυ αλληλων των λογισμων κατηγορουντων η κα απολογουμενων). Genitive absolute again showing the alternative action of the conscience, now accusing, now excusing. Paul does not say that a heathen's conscience always commends everything that he thinks, says, or does. In order for one to be set right with God by his own life he must always act in accord with his conscience and never have its disapproval. That, of course, is impossible else Christ died for naught (Galatians 2:21). Jesus alone lived a sinless life. For one to be saved without Christ he must also live a sinless life.