Pastor Martin Noland, a well known figure in today's LC-MS, disputes Pieper's writing and turns to a Jewish philosopher to find his ultimate "certainty". But here is Pieper's teaching based solely on Holy Scripture – the following is my own translation from Pieper's German (emphasis in original):
In the Preliminary Survey it has already been shown that faith of its object, namely, the grace of God, is certain, and indeed is divinely certain, because the grace of God is the object of faith and the seizing of this object is a divine effect in the human heart. The monstrum incertitudinis [monster of uncertainty] can only teach that faith should take its object, i.e. the Gospel, and set in its place the Gospel and Law or the whole of Scripture, or that faith is not a divine action, but a human self-determination, human self-decision, moral act, proper human behavior, etc. In fact, doubts can be found next to faith which remain in the hearts of Christians. But this doubt arises from the flesh that still clings to Christians, and is not to be praised with the Papists and synergists as a virtue, but rather as a sin to punish and to fight, 1 John 5:10. "He that believeth not God hath made him a liar; because he believeth not the record that God gave of his Son." (footnote reference: Chemnitz, Loci, De iustif., p. 270 f.)We see in this that Pieper also draws on the writing of another Martin, Martin Chemnitz. So Pastor Noland is not only refuting Franz Pieper but also Martin Chemnitz, the chief author of the Formula of Concord.
My translation varies only in minor ways from the English edition, but is perhaps more forceful... as Pieper is at his best in presenting the truly Lutheran teaching of the Certainty of Salvation. And the source of our certainty?... it is outside of us, it is "objective"... it is based entirely on God's certain promise that He had written down so that we might believe... and be certain. Do you like to be called a liar?...... neither does God.
This is how I console myself during the worldly "celebration"of Halloween... for I know who the real monster is, ... the real monster is far more deadly than any dreamed up monster of this world. And 1 John 5:10 is the perfect Bible verse to recite to oneself to destroy this monster! No amount of assurance that Pastor Noland dreams about can fight the true monster of uncertainty, rather God's Word is our sword of the Spirit (Eph 6:17).