Answer: Although the two observances occur on consecutive days and are closely related, they focus on different groups within the Communion of Saints. All Saints' Day on November 1 celebrates all those who have already attained Heaven, both the canonized saints and the countless holy souls known only to God. All Souls' Day on November 2 is devoted to prayers for the faithful departed who are still undergoing purification before entering Heaven. Together, the feasts express the Catholic belief in the spiritual bond between the saints in Heaven, the faithful on Earth, and the souls being purified. This distinction was reinforced when St. Odilo of Cluny established the November 2 commemoration around the year 998, placing it immediately after the celebration of all the saints on November 1.