This co-operation in our sanctification which God requires of us is composed of three parts. It consists first of all in the destruction of everything in our corrupt nature which is an obstacle to the divine action: sins, vices, sensible inclinations, defects, imperfections. This first labor is what the masters of the spiritual life call the _purgative way_. It is accomplished by examinations of conscience, works of penance and mortification, and the various practices in use in the Church. The second part of the labor which God imposes on the soul desirous to attain sanctity is less painful, and easier. It is what is called the _illuminative way_. The soul that God introduces therein exercises herself in producing the interior acts of virtue with which grace inspires her, and in practicing the good works to which this same grace impels her. Finally, when the obstacles are removed and the soul’s preparation is completed, God unites Himself to her, fills her with His grace, inflames her with His love, and uses her as a docile instrument for the accomplishment of His designs: this is the _unitive way_. But let us not misapprehend this condition. Even in this perfect state in which God is fully master of His reasonable creature, He does not act in her without her co-operation; He requires of her great fidelity in avoiding the smallest faults, great vigilance over her affections, great generosity in denying herself in all things, great fervor in prayer. So far from dispensing her from the works of the illuminative way by which she prepared herself for the divine union, He causes her to accomplish them with greater perfection and merit. Among these works common to the two ways of which we have just spoken, there are some which are strictly of obligation, either because they are prescribed to all Christians by the commandments of God and the Church, or because they are imposed on each one by the special circumstances of his state. There are others which are simply of counsel, or even purely of supererogation, and which each one embraces according to his more or less ardent desire of sanctification. In the same way, among the works of penance which form the purgative way there are some from which no one can dispense himself; but there are others which, without being of absolute necessity, are more or less useful, or even relatively necessary to certain souls, because of their particular position, and the violence of the inclinations which impel them to evil.