Romans 1:
20For from the creation of the world the invisible things of Him are clearly seen, being understood through the things that are made, even His eternal power and Godhead, so that they are without excuse.
Romans 2:
14For when the Gentiles, who have not the law, do by nature the things contained in the law, they, not having the law, are a law unto themselves,
15which shows the work of the law written in their hearts,their conscience also bearing witness, and their thoughts between accusing and excusing one another.)
16Thus will it be on the day when God shall judge the secrets of men by Jesus Christ, according to my Gospel.