Romans 1:18-20 [Jack J. Blanco's Clear Water paraphrase]
18. The consequences of not looking to God for help are seen in the lives of the Gentiles who generally don't care about doing what's right. Heaven can't bless people when they say that they believe the truth about the God of heaven and then live as they please.
19. They can know the truth about our God without us telling them. People are not that dull. They can see how God's laws work in nature. His laws are plain enough for everyone to see and understand.
20. So even though we can't actually see God, we can understand what He's like and how He governs by looking at nature. That's how it's been since the creation of this world. We can understand the regenerative power of God and His goodness by looking at the things He made, and that leaves people without excuse.