Meanwhile the Sacrament of Penance had become an integral part of the Roman sacramental system, and had replaced the earlier penitential discipline as the means by which the Church granted Christians forgiveness for sins committed after baptism. The scholastic theologians had busied themselves with the theory of this Sacrament. They distinguished between its "material," its "form" and its "effect." The "form" of the Sacrament was the absolution: its "effect," the forgiveness of sins; Its "material," three acts of the penitent: "confession," "contrition," and "satisfaction." "Confession" must be by word of mouth, and must include all the sins which the sinner could remember to have committed; "contrition" must be sincere sorrow of the heart, and must include the purpose henceforth to avoid sin; "satisfaction" must be made by works prescribed by the priest who heard confession. In the administration of the Sacrament, however, the absolution preceded "satisfaction" instead of following it, as it had done in the discipline of the early Church.[16] To justify this apparent inconsistency, the Doctors further distinguished between the "guilt" and the "penalty" of sin.[17] Sins were classified as "mortal" and "venial." [18] Mortal sins for which the offender had not received absolution were punished eternally, while venial sins were those which merited only some smaller penalty; but when a mortal sin was confessed and absolution granted, the guilt of the sin was done away, and with it the eternal penalty. And yet the absolution did not open the gate of heaven, though it closed the door of hell; the eternal penalty was not to be exacted, but there was a temporal penalty to be paid. The "satisfaction" was the temporal penalty, and if satisfaction was in arrears at death, the arrearage must be paid in purgatory, a place of punishment for mortal sins confessed and repented, but "unsatisfied," and for venial sins, which were not serious enough to bring eternal condemnation. The penalties of purgatory were "temporal," viz., they stopped somewhere this side of eternity, and their duration could be measured in days and years, though the number of the years might mount high into the thousands and tens of thousands.