In the middle of the journey of our life, I came to myself in a dark wood. - Dante Alighieri

This seeming incongruity has long troubled me. I owe Professor MacAllister a glad thanks for what is certainly the essential clarification. The whole Purgatorio, he points out, is built upon the structure of a Mass. The Mass moreover is happening not on the mountain but in church with Dante devoutly following its well-known steps. I have not yet had time to digest Professor MacAllister’s suggestion, but it strikes me immediately as a true insight and promises another illuminating way of reading the Purgatorio.

You taught me how a man becomes eternal;

Turn back and seek the safety of the shore; tempt not the deep, lest, losing unawares me and yourselves, you come to port no more.