2 Therefore of sin are unbelievers, that is, the lovers of the world, convinced; for they are signified by the name of the world. For when it is said, “He will convince the world of sin;” it is of none other sin than that they have not believed on Christ. For if this sin exist not, no sins will remain, because when the just man lives by faith, all are loosed. Now the difference is great as to whether one believe that Jesus is Christ, or whether he believe in Christ. For that Jesus is Christ even the devils believed, and yet the devils believed not on Christ. For he believes in Christ, who both hopes in Christ and loves Christ. For if he have faith without hope and love, he believes that Christ is, but he does not believe in Christ. Whoso then believes in Christ, by believing on Christ, Christ comes unto him, and in a manner unites Himself to him, and he is made a member in His Body. Which cannot be, but by the accession of hope and love.
Source: Sermons on Selected Lessons of the New Testament (New Advent)