I suppose I'd suggest three possible answers.
Though I've not read or thought of the Bible much.
One,
'Could argue that specific quote was speaking of 'history, rather than Paul telling people 'how to convert others.
Though I am not sure what the "demonstration of the Spirit and of power" 'was.
"1And I, when I came to you, brothers,a did not come proclaiming to you the testimonyb of God with lofty speech or wisdom. 2For I decided to know nothing among you except Jesus Christ and him crucified. 3And I was with you in weakness and in fear and much trembling, 4and my speech and my message were not in plausible words of wisdom, but in demonstration of the Spirit and of power, 5so that your faith might not rest in the wisdom of menc but in the power of God."
I further argue One, by
"11Therefore, since we know what it means to fear the Lord, we try to persuade men. What we are is clear to God, and I hope it is clear to your conscience as well. 12We are not commending ourselves to you again. Instead, we are giving you an occasion to be proud of us, so that you can answer those who take pride in appearances rather than in the heart."
Persuading is 'still spoken of.
Two, rather than the words of men, to focus on God,
Paul speaks of Christ as a foundation,
"Christ Our Foundation
10By the grace God has given me, I laid a foundation as an expert builder, and someone else is building on it. But each one must be careful how he builds. 11For no one can lay a foundation other than the one already laid, which is Jesus Christ.
12If anyone builds on this foundation using gold, silver, precious stones, wood, hay, or straw, 13his workmanship will be evident, because the Day will bring it to light. It will be revealed with fire, and the fire will prove the quality of each man’s work. 14If what he has built survives, he will receive a reward. 15If it is burned up, he will suffer loss. He himself will be saved, but only as if through the flames."
Rather than his 'own words and persuasion (Of man) being the focus, it is more important that 'Gods words and truth be spoken?
He speaks 'against exalting the 'messenger, above God, I think?
"God’s Fellow Workers
1Brothers, I could not address you as spiritual, but as worldly—as infants in Christ.
2I gave you milk, not solid food, for you were not yet ready for solid food. In fact, you are still not ready,
3for you are still worldly. For since there is jealousy and dissension among you, are you not worldly? Are you not walking in the way of man?
4For when one of you says, “I follow Paul,” and another, “I follow Apollos,” are you not mere men?
5What then is Apollos? And what is Paul? They are servants through whom you believed, as the Lord has assigned to each his role.
6I planted the seed and Apollos watered it, but God made it grow.
7So neither he who plants nor he who waters is anything, but only God, who makes things grow.
8He who plants and he who waters are one in purpose,
a and each will be rewarded according to his own labor.
9For we are God’s fellow workers; you are God’s field, God’s building."
Three
Spiritual truths,
What is meant by this?
Really I am unsure,
Is it meant as metaphysical?
Is it some 'stirring in the human condition?
Either way though, the third possibility I think of,
Is that Paul desires people's faith be of that experience, rather than reason.
. . .
Which 'can sound a bit bad,
But such a pull is human,
People can place or experience value in something, that contrary to evidence or reason,
They consider it worth the leap.
. . .
'Family, is such for myself.