Answer: The two things that we must believe are (1) that Jesus is the Christ, the Son of God, and (2) that because we believe that Jesus is the Christ, the Son of God, this belief (faith) also causes us to believe that we may have life in His Name, (verse 31).
MORE INFORMATION AND/OR OTHER SCRIPTURE REFERENCES:
Faith must contain Jesus Christ, the Son of God. Faith in Jesus Christ has a purpose, and that is life in His Name. His Name represents all that He is and stands for. In ancient times, an individual's name summed up his whole person:
Acts 4:12: "Salvation is found in no one else, for there is no other name under heaven given to men by which we must be saved."
Philippians 2:9-11: "Therefore God exalted Him [Jesus] to the highest place and gave Him the Name that is above every name, that at the Name of Jesus every knee should bow, in heaven and on earth and under the earth, and every tongue confess that Jesus Christ is Lord, to the glory of God the Father."
