By using the death of Jesus on the Cross, God has “made foolish the wisdom of this world” (v. 20). Where is the wise, scribe, the debater of this age? These three questions call on the highest educated (and potentially most arrogant) people in the Greek or Jewish world. There is a tone of derision: God has made your most educated look foolish when he saved people through the folly of the Cross.
God did not choose to save those who are perishing in a way that might be expected, by using a method the intelligent of the world would have given their approval. Rather, he chose to use the foolishness of the Cross. In other words, “God’s actions make the worldly-wise look like blundering fools” (Garland, 1 Corinthians, 63).
Execution by crucifixion was the most shameful death possible. If the Romans executed someone by crucifixion, they were guilty of the very worst of crimes and suffered such dishonor that it might even be shameful to admit you knew the person, let alone think they were your savior.
Paul begins this paragraph with the observation “Jews demand a sign, Greeks seek wisdom.” The Jewish “demand for a sign” refers to some sign from heaven which confirms a person is approved by God. If someone claimed to be the messiah, then Pharisees might demand they do some sort of sign, as they did Jesus. If Jesus could give them a sign to convince them he was the messiah, then perhaps they would believe. The point of the apostolic signs such as Peter healing a lame man in Acts 3 was to show the messianic age has begun.
A Greek would be far more likely to believe a well-constructed, logic argument in favor of Jesus as the Messiah. When Paul teaches in Ephesus, for example, he argues persuasively from the Scripture that Jesus is the Messiah; Apollos also persuades people from the Scripture through logical arguments (Acts 18).
The Messiah crucified was a stumbling-block to the Jews and a god who is executed as a criminal is foolishness to the Greek. Many Jews expected some sort of Messiah, but no one really expected a Messiah who would be executed by the Romans. The Gentiles were to fall under the judgment of the Messiah! He was to rule over a reunited Israel like an idealized David, no one expected him to die in the most shameful way possible. Peter response to Peter in Mark 8 is an indication that even Jesus’ followers misunderstood what the messiah would do in Jerusalem.
A “stumbling-block” is something that causes you to stumble (obviously), but Paul is using it as a metaphor. The cross is the thing that causes the Jewish person to not accept Jesus as the messiah and savior. They might like Jesus’ teaching, his way of handling the Law, his views about the kingdom of God, his rejection of oral tradition, etc. But most Jews would have a hard time accepting a messiah who was unjustly executed by the High Priest!
To the Greek or Roman thinker, it is not impossible for a god to appear to be flesh and live among humans for a time. Perhaps the more intellectual Greeks disbelieved the stories of Zeus or Hermes appearing as men, but it was at least possible. But it was impossible for a god to be harmed by humans, let alone be executed as the worst of criminals!
God chose to use the most foolish thing imaginable in the first century, the Cross, to save those who are perishing. God has always used the unexpected person to achieve his goals so that it is clear he has done it not human wisdom or skills (David as the youngest son, defeats Goliath, etc.) What God did through Jesus is to turn the world “upside down,” an idea Paul will return to throughout this letter.
The world sees the world one way, the Christian sees it much differently.