The Texts
"From the end of the earth I call to you when my heart is faint; lead me to the rock that is higher than I."
"He gives power to the faint, and to him who has no might he increases strength."
Isaiah 40:29–31 is the theological principle behind FC Ep II expressed in prophetic form. He gives power to the faint; to him who has no might He increases strength. Even youths shall faint and be weary, and young men shall fall exhausted, but they who wait for the Lord shall renew their strength. The passage does not describe a cooperative arrangement in which God supplies the difference between what a person can do and what the goal requires. It describes a movement from zero. The person who receives the strength had none; the one whose strength is renewed had exhausted every resource. Isaiah 40 is addressed to a people who have already discovered the absolute limit of their own capacity. FC Ep II's doctrine of conversion is the doctrinal form of that discovery: God gives to those who have nothing. Psalm 61:2's cry is the prayer of the person at that limit. "From the end of the earth I call to you when my heart is faint; lead me to the rock that is higher than I." The faint heart has reached the end of the earth, the boundary of its own resources, and calls from there. The rock it needs is higher than it is. It cannot climb to the rock; the rock must be the foundation to which it is led. FC Ep II's insistence that conversion is entirely the Holy Spirit's work is the doctrinal account of why Psalm 61's prayer is the right prayer: not God help me do my part, but lead me to the rock that is higher than I.
The Absolute Zero of Natural Spiritual Strength
FC Ep II's opening account of the natural will's condition is unsparing. In spiritual and divine things, the understanding and reason of fallen man are entirely blind. The unregenerate will is not merely turned away from God but has become an active enemy of God, desiring only what is evil and contrary to Him. The confessors declare that man is as utterly unable to raise himself to spiritual life as a physically dead body is able to quicken itself back to earthly life. Before conversion, man cannot by his own natural powers understand, believe, accept, think, will, begin, or cooperate in working anything toward his salvation, even in the least or most inconsiderable part. The comparison to a stone, a log, or a pillar of salt is meant to close every door through which a residual human contribution might enter.
FC Ep II says man cannot cooperate toward his salvation even in the least or most inconsiderable part. Isaiah 40 gives power to the faint, not to those with remaining reserves. How does a pastor preach the grace of conversion to a congregation that has absorbed the cultural assumption that everyone brings something to the table, and that dignity requires at least a minimal human contribution to any significant outcome?
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The Synergist Drift and Its Correction
The specific error FC Ep II was written to condemn is synergism as taught by Victorin Strigel and John Pfeffinger, who argued that while man is too weak to convert himself, he retains some residual powers. When the Holy Spirit offers grace, the human will can meet God halfway, qualify itself for grace, and yield a feeble consent. The Formula's rejection is total: even the feeblest assent, if it comes from natural human powers, is a human contribution to salvation and therefore a corruption of grace alone. The practical significance is not merely theological precision; it is pastoral. If salvation requires even a feeble human assent by natural powers, the terrified conscience can never know whether its assent was feeble enough to qualify or so weak as to be insufficient.
FC Ep II's condemnation of even a feeble assent by natural powers has a precise pastoral consequence: if assurance depends even minimally on the quality of a person's response, assurance can never be complete. Isaiah 40 gives strength to the faint precisely because the faint have nothing. How does a pastor address the person in his congregation who fears that her faith is not strong enough, decisive enough, or sincere enough for God to accept it, using FC Ep II's doctrine rather than exhorting her to try harder?
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When Cooperation Begins
FC Ep II is careful to define the boundary precisely: before conversion, man is pure passive and contributes nothing; after conversion, the regenerate will is not idle but cooperates actively with the Holy Spirit. Once the Spirit has wrought the new birth and renewed the will by divine power alone, the new will becomes an instrument and organ of God the Holy Spirit. After this renewal, we can and should cooperate with the Spirit, though in great weakness, and this cooperation is genuine and real. But it does not arise from native carnal powers; it arises entirely from the new powers and gifts the Holy Spirit has begun in the believer.
FC Ep II says cooperation begins only after conversion and only from the new powers the Spirit has given, not from native carnal powers. Isaiah 40 promises strength for running and walking to those who wait on the Lord. How does this precise boundary protect the Christian from two opposite pastoral errors: the error of passivity (I must wait for the Spirit to act; I can do nothing) and the error of self-reliance (I must work harder to produce the Christian life the Spirit wants)?