Romans 2:14-15

¹⁴ for when Gentiles, who do not have the law, by nature do the things in the law, these, although not having the law, are a law to themselves,

¹⁵ who show the work of the law written in their hearts, their conscience also bearing witness, and between themselves their thoughts accusing or else excusing them)

The Gentiles, without the law, still have consciences that make them feel guilt, but they make excuses to justify themselves.

Nature (v.1)  = natural impulse (in contrast to obedience to God’s decrees).

The law isn’t written in the Gentiles’ hearts, but the work of the law is, namely condemnation.

Conscience (v.2)  = knowledge of right and wrong. Conscience is to Gentiles what Law is to Jews, a guide for individual conduct and for relations with others.

Thoughts (v.2) = reasoning

Accusing and excusing both indicate guilt.

There is no justification in this passage, only condemnation.