Is more evidence necessary?

How many of us struggle with doubt? It could be that we just aren't sure, or we could completely reject. In Matt ch11, John the Baptist sends his disciples to ask Jesus if He is the one. Interesting that John needs this confirmation. After all, he recognized the "lamb of God" as Jesus when he baptized Jesus. He understood his place and rank next to Jesus, not being worthy to untie Jesus' sandals. So why the doubt? John is in prison, and perhaps hasn't seen God work in quite the fashion he expected. Sound familiar? God not working in the fashion we expect? It is taking too long, there doesn't seem to be any activity, etc. We doubt. We become uncertain. Check out Jesus' response in ch11v4-6. Do we need ANOTHER miracle to believe?