Romans 2:1 ¶ Therefore thou art inexcusable, O man, whosoever thou art that judgest: for wherein thou judgest another, thou condemnest thyself; for thou that judgest doest the same things.
Conscience is an important Bible word which is found in the New Testament not the Old. It means, “the faculty of moral consciousness or awareness by which moral judgments relating to right and wrong are made.” BDAG
Conscience begins with self-awareness, and moves to the innate recognition that right and wrong exist. This is more than learned socialization. It is an inseparable aspect of human consciousness. It is a state of being. It is the mark of our creator obligating us to be morally like Him.
This text is not opposed to judging, it is a warning of the self-indictment contained in the act of judging. When we judge another person we prove we have a conscience, can recognize the need for right thought and behavior, and we are confident enough in this knowledge to measure the moral state of someone else. We then, when judged by God, cannot plead that we did not know. We are, as the verse says, inexcusable.
The more detailed our knowledge of the precision of moral perfection the greater our own condemnation. This is why nearness to God never leads to arrogance... it leads to humility, and more dependence on the Gospel.
It is not obedience to a list of rules, but the purity of ourselves that conscience seeks. Our conscience may find temporary solace in an obeyable list of behavioral rules, but it can never by behavioral means fully free itself from the conscious weight of imperfection. That ever-present nudge of conscience that we are not as we should be is an indicator that we need something more than we have within us to be at peace with ourselves and our Creator. Jesus put the demand of conscience this way: “Be ye therefore perfect, even as your Father which is in heaven is perfect.” Matthew 5:48 Then... He gave us the Gospel.