Commentary Purg XVIII 19-21

Virgil, responding to Dante's request, carries his analysis of the loving human mind to the next level, the role of the rational soul in determining human choice and, therefore, action.  This tercet establishes the subject of Virgil's difficult clarification (vv. 22-39): how mind (the rational soul, created directly by God and instilled in the embryo last [see [Purg XXV 67-75]]) reacts appetitively to external things.