“What is your take on 1 Corinthians 7:40, where Paul says, ‘I think also that I have the Spirit of God’?”
The vast majority of things Paul taught in his epistles were things he himself had been taught by direct revelation of the Lord. However, he occasionally wrote things that the Lord had not revealed to him, such as:
“Now concerning virgins I have no commandment of the Lord: yet I give my judgment…” (1 Cor. 7:25).
The Corinthians had evidently asked Paul about something concerning which he had received no revelations, so he gave his own personal opinion. Of course, his opinion was molded by his understanding of all that God had revealed to him, so it would have been a very sound opinion. But when he then wrote it in an epistle that became part of God’s Word, that removed all doubt that his personal conviction expressed God’s will.
You see, it was the job of the prophets to identify which epistles were canonical (1 Cor. 14:37). Paul mentions some epistles that they did not include in the Scriptures (1 Cor. 5:9; Col. 4:16), but when they did include 1 Corinthians, that tells us Paul did have the Spirit when he wrote it, and that his own personal “judgment” was also the judgment of God. source