1 Corinthians 1:22-24 (NIV)
Jews demand miraculous signs and Greeks look for wisdom, but we preach Christ crucified: a stumbling block to Jews and foolishness to Gentiles, but to those whom God has called, both Jews and Greeks, Christ the power of God and the wisdom of God.
You can pretty much divide the world into three categories when it comes to what people think about Jesus Christ.
You've got the devoted religious crowd represented by the Jews here in this verse but anyone who is enamored with their religion would fit this category. This group is convinced that there is a God who created the world, no problem there. They are also usually convinced that the way they go about practicing religion is what gives them favor with God. To get them to move from their position you'd have to show them a miracle, a sign from God which they would readily believe. Although they believe in a creator god, they stumble over the idea that God would become a human and die to pay our sin debt, and then offer eternal life without any recognition of human merit.
And then you have the intellectual crowd, devoted to science and naturalism, who believe that anything supernatural is just so much foolish myth and superstition. The Greeks represent this group. They are very interested in philosophy and in understanding logic and how the world works. They mistake understanding of how something works with knowing how it actually came to be. You can't even get past first base with an intellectual who believes that the world just happened by random chance. If talk of a creator God is foolishness, talk of Jesus Christ is ever more so.
There is a third group here, represented by anyone who humbles himself before God's power and wisdom and becomes a fool for Christ.
I know, I'm a fool.
1 Corinthians 1:21 (NIV)
For since in the wisdom of God the world through its wisdom did not know him, God was pleased through the foolishness of what was preached to save those who believe.