A friend gave me some key words recently. He said Peter wrote about _Hope:_ "When the Chief Shepherd shall appear." The keynote of Paul's writings seemed to be _Faith_, and that of John's, _Love_. "Faith, hope and charity," these were the characteristics of the three men, the key-notes to the whole of their teachings. James wrote of _Good Works_, and Jude of _Apostasy_.
In the general epistles of Paul some one suggested the phrase "_in Christ_." In the book of Romans we find justification by faith _in Christ_. Corinthians presents sanctification _in Christ_. The book of Galatians, adoption or liberty _in Christ_. Ephesians presents fulness _in Christ_. Philippians, consolation _in Christ_. In Colossians we have completeness _in Christ_. Thessalonians gives us hope _in Christ_.
Different systems of key words are published by Bible scholars, and it is a good thing for every one to know one system or other.