The use of God given reason.
“Come now, let us reason together, says the LORD: though your sins are like scarlet, they shall be as white as snow; though they are red like crimson, they shall become like wool. (Isaiah 1:18)
“When he came to his senses, he said, ‘How many of my father’s hired servants have food to spare, and here I am starving to death!
(Luke 15:17)
For when Gentiles who do not have the Law do instinctively the things of the Law, these, not having the Law, are a law to themselves, in that they show the work of the Law written in their hearts, their conscience bearing witness and their thoughts alternately accusing or else defending them, (Romans 2:14-15)
And many, many more.