When Kant was still working on the Physical Monadology, a tsunami shattered the coastal city Lisbon (1 November 1755). Fires broke out in the chaos that merged into a firestorm incinerating the rubble. It was the worst earthquake recorded up to this point in Western history; 70,000 people died. It struck on Sunday, which happened to be a holiday (All Saints Day, Allerheiligen for Kant). The twelve-meter (40 ft) high waves slammed at the city churches just when the flocks had gathered. The impact destabilized the towers, which collapsed backwards for static reasons, crashing through roofs and crushing whoever prayed below. The brothels, located further up in the hills, were spared. The faithful died, and the sinners survived.  This posed a theological challenge.