The conversion and new life of the Corinthians were Paul's certificate as an apostle. They were a certificate known, he says, and read by all men. Often there is a certain awkwardness in the presenting of credentials. It embarrasses a man when he has to put his hand into his breast pocket, and take out his character, and submit it for inspection. Paul was saved this embarrassment. There was a fine unsought publicity about his testimonials. Everybody knew what the Corinthians had been, everybody knew what they were; and the man to whom the change was due needed no other recommendation to a Christian society. Whoever looked at them saw plainly that they were an epistle of Christ; the mind of Christ could be read upon them, and it had been written by the intervention of Paul's hand. This is an interesting though a well-worn conception of the Christian character. Every life has a meaning, we say; every face is a record; but the text goes further. The life of the Christian is an epistle; it has not only a meaning, but an address; it is a message from Christ to the world. Is Christ's message to men legible on our lives? When those who are without look at us, do they see the hand of Christ quite unmistakably? Does it ever occur to anybody that there is something in our life which is not of the world, but which is a message to the world from Christ? Did you ever, startled by the unusual brightness of a true Christian's life, ask as it were involuntarily, "Whose image and superscription is this?" and feel as you asked it that these features, these characters, could only have been traced by one hand, and that they proclaimed to all the grace and power of Jesus Christ? Christ wishes so to write upon us that men may see what He does for man. He wishes to engrave His image on our nature, that all spectators may feel that it has a message for them, and may crave the same favour. A congregation which is not in its very existence and in all its works and ways a legible epistle, an unmistakable message from Christ to man, does not answer to this New Testament ideal.