Justification by faith alone (sola fide)

The modern phrase faith alone has drifted a long way from what Luther asserted, and the drift runs in two directions at once.

First, justification is forensic. It is a verdict, a declaration that a person stands righteous before God, pronounced on the ground of what Christ did rather than of anything in the person. Luther's image is imputation: the righteousness is Christ's and is reckoned to the believer, who remains in himself a sinner. His formula was simul iustus et peccator, at once righteous and a sinner. This is a legal category and it is deliberately distinguished from the moral change that follows, which the Reformers called sanctification and which is real, progressive and never complete in this life. Catholic theology does not make the separation: for Trent, justification is a translation from one state to another in which grace actually makes the person righteous, so that the declaration and the transformation are one act.

Second, faith is trust, not assent to propositions and not a mental act performed as a condition. Luther described it as a living, busy, active thing, and insisted that it cannot fail to produce works any more than fire can fail to produce heat. His notorious addition of the word alone to his German rendering of Paul's sentence in Romans was defended on the ground that the sense required it, and his commentary on James, which says a man is justified by works and not by faith alone, was to call that letter an epistle of straw, a judgement later Lutheranism did not follow.

Works, on this account, are necessary as fruit and useless as ground. Nobody in the sixteenth-century argument held that a Christian may live as he likes; the question was whether what a person does contributes to the verdict, and Luther said it does not.

The Council of Trent issued its decree on justification in 1547. It affirmed that grace is prior and unmerited, that nobody can be justified by their own works or by the law, and that faith is the beginning and root of justification. It then condemned the formula by faith alone as the Reformers used it, on the ground that justification involves the infusion of grace by which a person is genuinely made righteous, and that this righteousness is increased by good works performed in grace, which therefore genuinely merit an increase.

The disagreement is real but it is narrower than the polemics of either side suggested. Both hold that salvation originates in God's unmerited favour. Both expect a transformed life. The difference is whether the transformation is part of justification or its consequence, and whether the works done by a person already in grace can be said to merit anything.

In 1999 the Lutheran World Federation and the Catholic Church signed a Joint Declaration on the Doctrine of Justification, stating a common confession that sinners are justified by grace alone through faith in Christ's saving work and not because of any merit on their part, and declaring that the sixteenth-century condemnations do not apply to the teaching of the partner as set out in the document. The World Methodist Council associated itself in 2006, the Anglican Communion and the World Communion of Reformed Churches subsequently.

The declaration did not dissolve the difference. It stated that remaining differences of language, theological elaboration and emphasis are tolerable, which is a real achievement and not the same as agreement. Confessional Lutheran bodies outside the Federation rejected it, and Catholic and Reformed theologians continue to dispute whether the underlying accounts of grace can in fact be reconciled or were merely described in terms broad enough to accommodate both.