People often think it takes lots of faith to heal through prayer. Apparently the first Christian apostles even thought so. When they implored Jesus, "Increase our faith," he told them that with faith as small as a tiny seed they could command a tree to uproot itself and jump into the sea, and it would do it (see Luke 17:5,6). With this deft response, Jesus completely dismissed the notion that their faith would have to come in large quantities. He directed their thought away from the amount of faith they possessed to the power that lay behind it.
The power of prayer, Jesus taught, is not so much in the faith of the one who prays, but in what one has faith in. He placed absolute faith in God, omnipotent Truth, as the healing power, and so does Christian Science. Jesus made clear that divine Truth can be known, understood, so that one's faith is not blind, but enlightened—and that this understanding comes through faithfully following his teachings. He said, "If ye continue in my word, then are ye my disciples indeed; and ye shall know the truth, and the truth shall make you free" (John 8:31, 32).
Note that Jesus said "the truth shall make you free," not that one's knowing of the truth makes one free.