Robo had an excellent post earlier with his 8 elements. Looking back in history, it is clear that the basis for being a Pilgrim has changed.
Based on my Catholic upbringing, I would imagine that in the Middle Ages Christian Faith was the primary motivation. Pilgrims must have firmly believed, as Christians, that the remains of St. James were truly in Santiago. Otherwise, why go there? Sacrifice would have been another critical element, as the journey would have been much longer for those traveling by foot than our current designated 30 days or so. For anyone undertaking the pilgrimage, they left everything and everyone behind for as long as it took to reach Santiago de Compostela and to return home by the same means. For the sick and poor, it might indeed have been the walk of a lifetime. And, this sacrifice, whether it be physical, emotional, monetary, would have been offered up for God's Graces. So, it was used to pay off a spiritual debt or as a down payment for your apartment in Heaven. That is why wealthy people often paid others to be Pilgrims in their name, similar to buying indulgences.
What qualifies us, today, as "Pilgrims" if we aren't Christian, or don't believe the story of St. James, or that we need to build credits for Heaven, and we can stay connected to home electronically, and if we can relatively easily recoup the costs and sacrifices endured during the journey? Perhaps in these modern, faster, more informed, and more mobile times it is indeed the Inner Journey that we undertake that makes us Pilgrims. As Colleen said, her Camino started the day she decided to Walk the Way. Mine too, two years ago.
So then, why continue to walk to Santiago if the earlier motivations no longer apply? Why not walk around your hometown 14 times instead? Inner Journeys don't require going to specific localities. That is where Robo's last element hits home. History! As reflective and feeling beings, part of being a Pilgrim may require connecting to those who walked The Way in the past. Mooncat