Luther: This One Doctrine

[I]n my heart there rules this one doctrine, namely, faith in Christ. From it, through it, and to it all my theological thought flows and returns, day and night; yet I am aware that all I have grasped of this wisdom in its height, width, and depth are a few poor and insignificant firstfruits and fragments.

--Martin Luther, preface to Galatians, quoted in Wilhelm Dantine, Justification of the Ungodly (trans. E. W. Gritsch and R. C. Gritsch; Saint Louis: Concordia, 1968), 13