On the 31st of October, 1517, which was the eve of the festival of All Saints, Martin Luther nailed a seminal document to the door of the Castle Church in Wittenberg. The catalyst for this action took place during Easter of the same year, when a Polish monk by the name of Johann Tetzel, swept through the town of Juterbog, Germany selling indulgences.

Tetzel had been contracted by Prince Albert of Brandenburg, who, in an attempt to buy the Archbishopric of Mainz had taken out a significant loan from the Imperial Bankers in Augsburg to the tune of 48,000 ducats (roughly $7 million in today's currency). Albert paid the Pope the money he had borrowed from the bank, secured the title of Archbishop of Mainz, and then dispatched Tetzel to sell indulgences so he could raise the money to pay off his debt.

Tetzel marched into small towns and big cities alike throughout Germany, setting up his big banners with depictions of hellfire and generally scaring the peasants into parting with their coins. His famous phrase was "When the coin in the coffer rings, the soul from Purgatory springs"

When Luther got word of what was happening, he was incensed and he immediately penned 95 theses or arguments against the doctrine of indulgences. It was a tour de force of theological writing and struck at the very heart of the church's doctrine of dispensing grace for merit and profit.

According to eye-witness accounts, Luther nailed one copy of the theses to the door of the Castle Church and sent another copy directly to Prince Albert, who was by then, well and truly the Archbishop of Mainz.

Why make such a massive statement on All Saints Eve? Well, Prince Frederick of Saxony, who happened to be Luther's patron and employer, had a collection of close to 5,000 relics that pilgrims from all over Saxony came to see. In fact, they paid for the privilege to see these relics and in doing so bought themselves or their loved ones, time off Purgatory.

In addition to silver, which was mined in the hills of Saxony, Prince Frederick's relics were one of the biggest sources of revenue for the kingdom. The relics were displayed throughout the All Saints Festival and it was then that pilgrims converged on Wittenberg in droves to pay homage to the sacred objects.

Among Prince Frederick's relics were, supposedly, a thorn from the crown Christ wore on the cross, a splinter from Noah's Ark, and a piece of Moses' burning bush. Each relic was housed in a reliquary and put on display inside the Castle Church, which is what made Luther's choice of where to nail his 95 theses significant.

When Luther nailed his 95 theses to the door, he threw down a gauntlet before the entire organized system of religion in Christendom. It was both a challenge and a plea and it set in motion one of the most definitive movements in history.