The grace of justification, commonly called sanctifying grace, is related to actual grace as an end to its means. Actual grace introduces the state of sanctifying grace or preserves and augments it where it already exists.

This fact makes it advisable to consider the genesis of sanctifying grace before studying its nature and effects.

We shall therefore treat in three chapters: (1) of the Process of Justification (iustificatio in fieri); (2) of the State of Justification (iustificatio in esse), and (3) of the Fruits of Justification (iustificatio in facto esse), or the Merit of Good Works.