…. [Michelangelo’s] next work displays a grasp of human anatomy seldom seen in the history of art: a Pietà, his first but hardly his last interpretation of the subject. The Italian word has many grades of meaning: pity, compassion, mercy, piety, devotion. Capitalized, however, it refers to a scene not found in the gospels but considered by medieval piety to be appropriate to the biography of Jesus: after the dead Jesus was taken down from the cross and before he was entombed by Joseph of Arimathea, it was imagined that his body would have been laid in the arms of his mother, Mary, who had followed him to his crucifixion (at least as reported in John’s Gospel). This unlikely scene is made even more unlikely by the difficulty of setting a grown man’s body in the lap of his (presumably) smaller and weaker mother. The medieval attempts at illustration are invariably awkward and unconvincing.

      Michelangelo’s solution is extraordinarily clever, to such an extent that viewers are seldom aware of the visual trickery. Jesus is slightly smaller than his mother, but her draperies and her wide-kneed position successfully mask that reality. Moreover, the body of Jesus, slouching loose-limbed in an intensely realistic imitation of death, serves—along with Mary’s pose and her ample skirts—to attract our attention and to further mask the difference in the respective weights of the two figures. Perhaps even more important, the anatomy of Jesus is so exquisitely detailed as to demand soon enough almost our whole attention. But if that attention should stray, it will inevitably stray to Mary’s once-nurturing breasts, emphasized by the cross-band that slices through them and by the gathered cloth, and to Mary’s ever youthful but spiritual face, just bending forward over the body, resigned but—mysteriously enough—not inconsolable. She knows what has happened and why this was necessary.

      Michelangelo was twenty-three when he finished this Pietà. His contempt for human self-indulgence and his sense of the need for human suffering will only grow as he ages. But it is worthy of note that this most loyal Platonist of all Renaissance artists, loving the reality of symbols, eschewing the follies of the flesh, is also an intensely loyal Christian, whose reverence for the episodes of the gospels and whose belief in the reality of of the Redemption can be second to none. It is also worthy of note that Michelangelo’s piety takes at times an almost northern European turn. Before his Pietà, this grouping had been found almost exclusively north of the Alps, where it was called das Vesperbild (the Evening Image). As the respected contemporary critic Lutz Heusinger, professor of art history at Marburg, the original German Lutheran university, has written: “North of the Alps… the portrayal of pain had always been connected with the idea of redemption.” If Michelangelo’s Tuscan Platonism gives his Pietà a sinuosity that would be impossible for any German artist of this period, we should still bear in mind that Michelangelo’s mind and heart were open to very non-Italian and, from a strictly Roman Catholic viewpoint, dubiously orthodox Christina influences.

– Thomas Cahill, Heretics and Heroes: How Renaissance Artists and Reformation Priests Created Our World, 111-112