MORAL TOPOGRAPHY.--Within the gate is Purgatory proper with its seven terraces, each devoted to the purgation of one of the seven capital sins, “out of which other vices spring, especially in the way of final causation” (Aquinas). Whereas in the _Inferno_ sin was considered in its manifold and multiform effects, in the _Purgatorio_ it is regarded in its causes, and all referred to disordered love. The formal element, the aversion from the imperishable good, which is the essence of Hell, has been forgiven; the material element, the conversion to the good that perishes, the disordered love, is now to be purged from the soul. In the allegorical or moral sense, since love, as Aquinas says, is “the ultimate cause of the true activities of every agent,” it is clear that man’s first duty in life is to set love in order; and, indeed, the whole moral basis of Dante’s Purgatory rests upon the definition of St. Augustine that virtue is _ordo amoris_, “the ordering of love.” In the first three terraces, sins of the spirit are expiated; in the fourth terrace, sloth, which is both spiritual and carnal; in the fifth, sixth, seventh terraces, sins of the flesh. This purgation, which involves both pain of loss for a time and punishment of sense, is effected by turning with fervent love to God and detesting what hinders union with Him. Therefore, at the beginning of each terrace, examples are seen or heard of virtue contrary to the sin, in order to excite the suffering souls to extirpate its very roots; and, at the end, examples of its result or punishment (the “bit and bridle”). These examples are chosen with characteristic Dantesque impartiality alike from Scripture and legend or mythology; but, in each case, an example from the life of the Blessed Virgin is opposed to each capital sin. At the end of each terrace stands an Angel--personification of one of the virtues opposed to the sins or vices. These seven Angels in their successive apparitions are among the divinest things of beauty in the sacred poem. It is only when sin is completely purged away that man can contemplate the exceeding beauty, the “awful loveliness” of the contrary virtue.