In his book The Fourth Gospel (p. 100), Louis Bouyer comments on the healing of the paralytic at the pool of Bethesda (John 5:2-16): “The way in which Jesus works the cure reveals well how St. John understands faith. Jesus said: ‘Rise, take up thy pallet and walk,’ and the man does so. The other evangelists have similar details, but St. John dwells specially on [the aspect of faith]. For him faith, far from obviating activity on the part of man, includes it as an essential element. Faith is by no means pure passivity; on the contrary it requires action from us, but also a realization that by ourselves we are absolutely incapable of it, and therefore [we need] a total reliance on God. Just when the paralytic has given vent to his despair of ever being cured Jesus commands him to act as if he were [already made whole]: he attempts it, having only the speaker’s word.”
Bouyer points out that the same pattern of faith in Christ in the face of human impossibility has already occurred several times in John’s gospel: the healing at Capernaum of the official’s son who is on the point of death; the miracle of water changed to wine at Cana; the human impossibility of Jesus giving water to the Samaritan woman. In all of these narratives, St. John is demonstrating that the impotence of “human nature left to its own natural resources” is met by the power of God when people believe in Christ.
Most importantly, this portrayal of human weakness and divine power extends to the moral sphere as well, and Bouyer says that here we find “the hub of Christian life; a purely gratuitous gift of God, but one fully real, making of us new-born beings.” The Christian who is nothing in himself can now by faith in Christ do what he could not do before, because “God is the author of what takes place within him.” Should the person lose faith, however, it would be a matter of “falling back on himself and on his own nothingness instead of resting on God.”
In John 6, some of those who were following Jesus, and listening to his preaching, wanted to know how to live their lives in a way pleasing to God. They asked the Lord, “What must we do, to be doing the works of God?” (vs. 28) Based on the same truth that God is the author of all the good within them – of all their good willing and doing (cf., Phil 2:12-13) – Jesus said to them in reply, “This is the work of God, that you believe in him whom he has sent” (vs. 29). What they, and we, are incapable of by ourselves calls for a faith of total reliance on God. What is more, our incapability also means that even such a faith is itself a gift moved in us by God.