The intelligibility (and hence the persuasiveness) of Christian faith springs not from independently formulated criteria, but from compelling renditions, faithful performances.
Faith as such cannot contribute anything to our justification: bringing nothing of our own to procure the grace of God. It is not a habitus. It is not a quality of grace which is infused into man. Faith does not justify by virtue of being a work which we do. If we believe, we come to God quite empty, not bringing to God any dignity or merit. God has to close his eyes to the feebleness of our faith, as indeed He does. He does not justify us on account of some excellence which it has in itself; only in virtue of what it lacks as a human work does He justify man. For that reason there is no point in inquiring as to the completeness of our faith. Exegetes who understand the reckoned of Gen 15.6 as follows: Abraham has been reckoned righteous, and that belief in God was a virtue which he possessed are condemned by Calvin quite freely and frankly: those dogs must be an absolute abomination to us, for these are the most enormous blasphemies which Satan could vomit forth. As if there were nothing worse than this confusion! And, indeed, according to the fresh Reformation understanding of the Pauline justification by faith there could not be anything worse than this confusion. It is clear that if faith was to be a virtue, a power and an achievement of man, and if as such it was to be called a way of salvation, then the way was opened up for the antinomian and libertarian misunderstanding, the belief that a dispensation from all other works was both permitted and commanded. And the objection of Roman critics was only too easy, that in the Reformation sola fide this one human virtue, power and achievement was wildly over-estimated at the expense of all others. Even at the present day there is still cause most definitely to repudiate this misinterpretation, for which the Pauline text is not in any sense responsible.