Why would people observe a day that honors pagan gods by associating it with Christian saints?
The ancient Romans worshipped gods and goddesses involved with every aspect of life. Jupiter, the chief of the gods, was the deity of rain and storms, while his wife, Juno, was the goddess of womanhood. Minerva was the goddess of handicrafts and wisdom; Venus, of sexual love and birth; Vesta, of the hearth and sacred fires; Ceres, of farming and harvests.
The Greeks considered Mercury to be the messenger of the gods, but the Romans worshipped him as the god of trade, and businessmen celebrated his feast day to increase profits. Others included Mars, god of war; Castor and Pollux, gods of sea travelers; Cronos, the guardian of time; and Cupid, god of love, whose magic arrows encouraged humans and immortals to fall in love. The list goes on and on.
Romans would generically call on "the gods," but each deity had its own cult, and worshippers would pray and conduct religious ceremonies to a specific god or goddess to ask for help. Christianity, with its emphasis on one God, was viewed by many Romans as a strange superstition or even a kind of atheism that denied the existence of the gods.
Members of the early Christian Church considered themselves "saints," meaning holy or separated to God. Paul greets the church at Philippi as "all the saints in Christ Jesus" (Philippians 1:1). However, it wasn't long before "saints," in the Roman tradition, began to take on the meaning of a special class of martyrs or performers of heroic virtue.
In the second and third centuries it became common for congregations to honor the death of a martyr by celebrating the anniversary of his or her demise. The local cult would offer prayers to the dead for intercession with God. A "saint" could eventually receive universal recognition by declaration of the bishop of Rome .
The Catholic Encyclopedia explains: "As was taught by St. Augustine ... Catholics, while giving to God alone adoration strictly so-called, honor the saints because of the Divine supernatural gifts which have earned them eternal life, and through which they reign with God in the heavenly fatherland as His chosen friends and faithful servants.
"In other words, Catholics honor God in His saints as the loving distributor of supernatural gifts. The worship of latria...or strict adoration is given to God alone; the worship, or dulia...or honor and humble reverence, is paid the saints; the worship of hyperdulia...on account of her greater excellence, [is directed] to the Blessed Virgin Mary" (Vol. II, "Saints," 1907, Online Edition, 1999, Kevin Knight).
The evolution from the early Church's recognition of all members being saints to the veneration and worship of the dead is rooted in the early mixture of paganism with Christianity. The populace throughout the Roman Empire was accustomed not only to the worship of the Greek and Roman pantheon, but to cultic worship of local deities. It was an easy step for Christian congregations rooted in paganism to replace the customs of local cults with the worship of dead martyrs.
Over the centuries the Catholic Church canonized saints for many events, problems, illnesses and occupations, each celebrated with his or her own feast day. St. Stephen is the patron saint of stonemasons; doctors can pray to St. Luke, fishermen to St. Andrew and carpenters to St. Joseph. Patron saints are there for farmers, hunters, shoemakers and even comedians. The primary saint in Catholic theology is Mary, the mother of Jesus.