I was reading 1st Corinthians today, and found this great verse: "And my speech and my message were not in plausible words of wisdom, but in demonstration of the Spirit and of power, that your faith might not rest in the wisdom of men but in the power of God." (1st Corinthians 2:4-5, italics added)
Paul used miracles to show the Corinthians the power of God and the Holy Spirit. But it doesn't take a miracle to show power. One of the greatest miracles of Christianity is the change in our hearts when we are saved. If we live to be like Jesus, our witness can show unbelievers the power of the Spirit. I think this might be one reason for the Church's decline in Europe and America. When a nonbeliever sees poor people starving on Skid Row just miles from Orange County, where Christians drive Porsches and watch cable TV on their plasma TVs, he can't help but see the hypocrisy of our uncompassionate use of wealth. Perhaps if more Christians used their wealth (trust me, if you're on the Internet reading my blog, you're wealthy compared with the rest of the world) compassionately, our witness would help show nonbelievers the power of God. As it is, we try to use "the wisdom of men", not "the power of God" in our evangelistic outreaches.