The light of the world: Matthew and John and the meaning of faith

One passage in Matthew jumped out at me while I was reading. Matthew 5:14 reads “You are the light of the world.” A very simple phrase but it instantly reminded me of John 8:12 “Again Jesus spoke to them saying, ‘I am the light of the world’.” To me the comparison of the two sentences in very interesting. Both are supposedly spoken by Jesus to his followers, both are the same except for two words, yet these two sentences hold very different religious meaning. To say that some one is the light of the world, I tend to believe means that they are so full of God’s presence and grace that they stand as an undeniable example of God’s work in the world. They are a living example of God’s grace. Thus to have Jesus tell those that followed his teachings that they were living examples of God love is very very different from a Jesus who proclaims that he is the leaving example of God’s love and only through him can people truly experience God. The sentence that comes after 4:12 is “A city on a hill can not be hid” while the next sentence in John is “Whoever follows me will never walk in darkness but will have the light of life”. While Matthew seems to be urging Christians to be living examples of God’s love so that all might see them and be moved, John seems to be saying that only Jesus contains God’s light and only though belief in his divinity can one find God.
However I guess both passages are really speaking to faithfulness. What does it mean to be faithful to Matthew or to John? I think the two quotes illustrate what faithfulness means in these two gospels perfectly. For Matthew to be faithful is to fulfill God’s law, to become as it were like God in striving for a superhuman level of moral perfection. Matthew’s Jesus wants us to go beyond the law, and become the new law, one that channels God’s grace directly and allows it to affect every aspect of ones life. Matthew’s Christ is not interested in exact, obsessive adherence to the law as it is written only obsessive adherence to its spirit and the spirit of God’s divine love and grace. John on the other hand is involved in a completely different theological question, is Jesus Christ God come to Earth and if so how should we respond to him? Therefore to John being faithful is believing totally and utterly in Jesus’ divinity and trusting in him that he will save those who truly believe. For John then faithfulness is this complete trust in Jesus’ and a willingness to give one’s life for him.