Faith in Christ is more than simple intellectual certainty about the Divine Hypostasis of the incarnate Son and Logos of God. Intellectual certainty about the two perfect natures of the Lord Jesus Christ is only one aspect of the all-embracing reality that constitutes faith in Him.
God sent His Son into the world so that each of us might become a child of God (Gal. 3:23ff.). Hence our adoption by the Heavenly Father is dependent on our union with His Son. Christ invites each of us to unite with Him, first and foremost by following Him in keeping His commandments, as His Disciples were the first to do (Matt. 4:18ff.).