Joel R. Beeke: Christ's righteousness, alien to the believer, is the formal cause of justification, and faith is the instrumental cause

Joel R. Beeke explains that faith is the instrumental cause of justification and that Christ's righteousness -- alien to the believer and imputed to him -- is the formal or meritorious cause, the ground upon which we are justified:

Protestant theology, on the other hand [set against Romanism], maintained that faith is the instrumental cause of justification, while the alien righteousness of Christ, external to the believer and imputed to him, is the formal cause, i.e., the ground upon which God can justly justify sinners. ‘For he hath made him to be sin for us, who knew no sin; that we might be made the righteousness of God in him’ (2 Corinthians 5:21; cf. Romans 3:26). It is critical to maintain that this formal cause of justification resides in Christ’s righteousness alone, for all the Scriptures dealing with the fundamentally depraved nature of man make clear that there is no righteousness inherent in the natural man upon which a divine verdict of justification could be based. ‘They are all gone aside, they are together become filthy; there is none that doeth good, no, not one’ (Psalm 14:3). For the Reformers, faith was the conscious, personal immediate reliance of a sinner on Christ alone. (Dr. Joel R. Beeke, Justification by Faith Alone, Soli Deo Gloria (1995), p. 90)