Someone may think that he or she can reason without Divine revelation. In fact, such claims are the norm. No one seems to want to think that human beings are dependent on God. This is a topic of great importance. It should be approached without emotion and with the covering of the Holy Spirit.
Not only Atheists, but Christians sometimes think that they can reason without Divine revelation. One such Christian tried to give the scripture by which he thinks that God gave is the ability to discern truth: “Sure, when the Bible tells us to give a defense, test prophecies, and, perhaps, follow the lead of Paul who debated with Greek thinkers on their turf in their terms.”
There’s no evidence of an absence of God’s leading in giving a defense, especially looking at the original language meaning of defense and the context of the verse. In fact, it seems as if we are to speak Christ Himself, the One Who lives within us. There’s no leaning on our own understanding when testing prophecies. There’s no implication that this is done with the fallen natural mind and the assumptions that it dreams up. There’s nothing that says that Paul wasn’t led by the Spirit and speaking by the power and authority of the Holy Spirit.
This particular conversation was centered on speculative theology. The main reason that any Christian would lean on his or her own understanding is defense of doctrines that are contrary to what God is saying. They find it beneficial to add to what God is saying or diminish what God is saying. So, they add assumptions and stories. They reason using speculation and conjecture. They divide brother against brother and sister against sister.
If you think that you can riddle out understanding with the human mind, can you give the Scripture by which you think that God gave us the ability to discern truth without receiving discernment from Him?