What do the Jews require and the Greeks seek, and why does that cover all of humanity?

The Jews require a sign, and the Greeks seek after wisdom. These represent the two major categories of humanity, Jew and Gentile, so together they cover everyone. Paul does not pay attention to either demand but preaches Christ and the cross, which transforms those who believe.

Les explains that the passage says the Jews require a sign and the Greeks seek after wisdom. These are the two major categories of the human race, Jew and Gentile, so all people are covered. The Jews want signs; the Gentiles want highly educated philosophers. But Paul says we don't pay attention to either one. We preach Christ—not merely Jesus walking the highways of Palestine, walking on water, feeding the 5,000, or raising Lazarus—but the Christ who is the answer to the sin problem and imparts eternal life. Through the foolishness of preaching, the preaching of the cross, the gospel transforms those who believe, faith plus nothing.

1 Corinthians 1:22

For the Jews require a sign, and the Greeks seek after wisdom:

Why did the Jews require a sign but the Gentiles did not?

Signs meant everything to the Jew but didn't mean that much to Gentiles; Greek philosophers sought wisdom instead. Paul preached Christ crucified rather than relying on signs to convince Jews or philosophy to convince Greeks, and he taught that preaching the Word, not miracles, is what people need.