What then is the part assigned to faith in justification? According to Luther
(and Calvin also), the faith that justifies is not, as the Catholic Church
teaches, a firm belief in God's revealed truths and promises (fides theoretica,
dogmatica), but is the infallible conviction (fides fiducialis, fiducia) that
God for the sake of Christ will no longer impute to us our sins, but will
consider and treat us, as if we were really just and holy, although in our inner
selves we remain the same sinners as before. Cf. Solid. Declar. III, sec. 15:
"Through the obedience of Christ by faith the just are so declared and reputed,
although by reason of their corrupt nature they still are and remain, sinners as
long as they bear this mortal body." This so-called "fiduciary faith" is not a
religious-moral preparation of the soul for sanctifying grace, nor a free act of
cooperation on the part of the sinner; it is merely a means or spiritual
instrument (instrumentum, organon leptikon) granted by God to assist the sinner
in laying hold of the righteousness of God, thereby to cover his sins in a
purely external manner as with a mantle. For this reason the Lutheran
formularies of belief lay great stress on the doctrine that our entire
righteousness does not intrinsically belong to us, but is something altogether
exterior. Cf. Solid. Declar., sec. 48: "It is settled beyond question that our
justice is to be sought wholly outside of ourselves and that it consists
entirely in our Lord Jesus Christ." The contrast between Protestant and Catholic
doctrine here becomes very striking. For according to the teaching of the
Catholic Church the righteousness and sanctity which justification confers,
although given to us by God as efficient cause (causa efficiens) and merited by
Christ as meritorious cause (causa meritoria), become an interior sanctifying
quality or formal cause (causa formalis) in the soul itself, which it makes
truly just and holy in the sight of God. In the Protestant system, however,
remission of sin is no real forgiveness, no blotting out of guilt. Sin is merely
cloaked and concealed by the imputed merits of Christ; God no longer imputes it,
whilst in reality it continues under cover its miserable existence till the hour
of death. Thus there exist in man side by side two hostile brothers as it were —
the one just and the other unjust; the one a saint, the other a sinner; the one
a child of God, the other a slave of Satan — and this without any prospect of a
conciliation between the two. For, God by His merely judicial absolution from
sin does not take away sin itself, but spreads over it as an outward mantle His
own righteousness. The Lutheran (and Calvinistic) doctrine on justification
reaches its climax in the assertion that "fiduciary faith", as described above,
is the only requisite for justification (sola fides justificat). As long as the
sinner with the "arm of faith" firmly clings to Christ, he is and will ever
remain regenerated, pleasing to God, the child of God and heir to heaven. Faith,
which alone can justify, is also the only requisite and means of obtaining
salvation. Neither repentance nor penance, neither love of God nor good works,
nor any other virtue is required, though in the just they may either attend or
follow as a result of justification. (Cf. Solid. Declar, sec. 23: "Indeed,
neither contrition nor love nor any other virtue, but faith alone is the means
by which we can reach forth and obtain the grace of God, the merit of Christ and
the remission of sin.") It is well known that Luther in his German translation
of the Bible falsified Romans 3:28, by interpolating the word "alone" (by faith
alone), and to his critics gave the famous answer: "Dr. Martin Luther wants it
that way, and says, 'Papist and ass are the same thing: sic volo, sic jubeo, sit
pro ratione voluntas'."

Since neither charity nor good works contribute anything towards
justification — inasmuch as faith alone justifies — their absence subsequently
cannot deprive the just man of anything whatever. There is only one thing that
might possibly divest him of justification, namely, the loss of fiduciary faith
or of faith in general. From this point of view we get a psychological
explanation of numerous objectionable passages in Luther's writings, against
which even Protestant with deep moral sense, such as Hugo Grotius and George
Bull, earnestly protested. Thus we find in one of Luther's letters, written to
Melancthon in 1521, the following sentence: "Be a sinner and sin boldly, but
believe and rejoice in Christ more strongly, who triumphed over sin, death, and
the world; as long as we live here, we must sin." Could anyone do more to
degrade St. Paul's concept of justification than Luther did in the following
blasphemy: "If adultery could be committed in faith, it would not be a sin"?
(Cf. Möhler, "Symbolik", sec. 16). The doctrine of justification by faith alone
was considered by Luther and his followers as an incontrovertible dogma, as the
foundation rock of the Reformation, as an "article by which the Church must
stand or fall" (articulus stantis et cadentis ecclesia), and which of itself
would have been a sufficient cause for beginning the Reformation, as the
Smalkaldic Articles emphatically declare. Thus we need not wonder when later on
we see Lutheran theologians declaring that the Sola-Fides doctrine, as the
principium materiale of Protestantism, deserves to be placed side by side with
the doctrine of Sola-Scriptura ("Bible alone", with the exclusion of Tradition)
as its principium formale — two maxims in which the contrast between Protestant
and Catholic teaching reaches its highest point. Since, however, neither maxim
can be found in the Bible, every Catholic is forced to conclude that
Protestantism from its very beginning and foundation is based on self-deception.
We assert this of Protestantism in general; for the doctrine of justification as
defended by the reformed Churches differs only in non-essentials from
Lutheranism. The most important of these differences is to be found in Calvin's
system, which taught that only such as are predestined infallibly to eternal
salvation obtain justification, whilst in those not predestined God produces a
mere appearance of faith and righteousness, and this in order to punish them the
more severely in hell (Cf. Möhler, "Symbolik", sec.12).