Though the term "justification" may be extended to the preparatory acts that lead up to the state of justice, strictly speaking it signifies only that decisive moment in which the sinner is cleansed from mortal sin by an infusion of sanctifying grace. Hence a careful distinction must be made between justification as an act (actus iustificationis) and justification as an habitual state (habitus iustificationis s. status gratiae sanctificantis). The transient act introduces a permanent state, just as the Sacrament of Holy Orders constitutes a man in the sacerdotal state or priesthood.

Both as an act and as a state justification possesses three distinct properties; it is uncertain, unequal, and capable of being lost.

This gives us the basis for a division of the present Chapter into three Sections: (1) On the Nature of Justification, (2) On Justifying, i.e. Sanctifying Grace, and (3) On the Properties of that Grace.