Saul the Pharisee makes a triumphant return in the first part of this chapter (subtitled "Warnings from Israel's past" by NIV), and it's not a bad thing. The Pharisee movement can be roughly traced from Ezra the priest who led Israel back from captivity, and who like Nehemiah tore out his hair upon learning that, once AGAIN, the men of Israel were taking foreign wives - the sin of Solomon and the open gateway to grassroots family-by-family idolatry. At its foundation, Phariseeism was a well-intentioned, determined effort to eliminate the nation's besetting sin.
In the same way Guy the Teenage Unitarian puts in his two-cents worth to my present decision-making. Sometimes he offers good insights that inform my Christian walk. I think Paul himself would be the first to say that his ministry, and the church of Christ, can learn from the past once the Lordship of Christ is firmly established.
Back to Corinthians - Saul the Pharisee tells the church, "flee idolatry. Look what happened when Israel didn't." He does NOT say "separate yourself physically from all Unholiness and spit on those who don't." He takes a more radical view than mere physical separation. He preaches freedom of conscience, humility, and individual and corporate eternal vigilance of our desperately wicked hearts. And in an encouraging way he bids us to humbly rely on divine Providence:
"So, if you think you are standing firm, be careful that you don’t fall! 13 No temptation[c] has overtaken you except what is common to mankind. And God is faithful; he will not let you be tempted[d] beyond what you can bear. But when you are tempted,[e] he will also provide a way out so that you can endure it."
Unlike the Pharisees, in Christ there is no condemnation. Neither is there boasting, save in Christ. God will make a way, where there is no way, only trust and obey. Paul uses different words than Jesus, but like a good soldier of his Savior and Lord he brushes past the useless Maginot Line of good works and appearances and marches straight for the real battlefield: the hearts and minds. His weapons are the living gospel and the Spirit of the God. And although he sees further than I about the details of the Kingdom Triumphant, I don't think he really knew what total victory would look like. As he says elsewhere, "No eye has seen, no ear has heard, what God has prepared for those who love Him."