One of the important things to appreciate is that the earliest centuries of the church, and even the church in some parts of the world today, inhabited a world imbued with divinities and supernatural activity. People were less likely to attribute goings on in their lives or the world to vast impersonal forces or to the randomness of life. The agency of God or gods, demons, and saints was very real. When something happened, people were ready to attribute religious significance to it in a way that people in modern secularized societies are not.

Individuals considered saints were said to meet certain standards of holiness, and attained a reputation for this kind of holiness during their lifetimes. Cults have even developed around certain very holy individuals within their own lifetimes. Many of the earliest people venerated were those indisputably connected with stories in the Bible, people like Mary, the Apostles, John the Baptist, and Stephen the Protomartyr. Feast days and nativities were honored, and their names could be included in liturgical litanies. Subsequent saint cults grew up organically as well, and in many cases inconsistently. The modern bureaucratic system by which the Vatican beatifies and canonizes the departed is, in relative terms, a recent development.

On what terms, then, would somebody be considered a saint? People who were considered exceptionally faithful and obedient Christians were the best candidates, and being known as a martyr helped a great deal. These saint cults tended to be of a local character, and did not always become generalized to the entire church. If a holy person died, and people began attributing miracles to the intercession of that person, they could be considered a saint. This was especially the case if the faithful came to associate miraculous cures or other interventions to the saint's relics, or if miracles were said to occur at the saint's tomb. St. Gregory of Tours, for example, reports that St. Martin miraculously cured a man of blindness who went to his shrine, and then struck him blind again for engaging the services of a Jewish physician. At the execution of St. Cyprian of Carthage, the faithful were prepared with pieces of cloth to catch drops of his blood; anything from a holy man's body was highly prized. If Christians attributed miracles to your intercession with God, you could be made a saint. This was frequently a process initiated by the laity and then confirmed by a local bishop later on. The exact process behind how local saint cults came to be adopted by the church as a whole is actually quite hazy prior to the Renaissance.

There are so many saints at this point that accounting for all of them is difficult, and there is more evidence for some of them existing than for others. What mattered, and still matters, to believers is that the merits of that particular saint imbue their prayers with unique intercessory powers. We may not necessarily believe all of the saint stories today, but lay piety has for a long time encouraged believers to look to the example of holy men and women, and their example has been quite powerful.

Readings

Robert Bartlett, Why Can the Dead Do Such Great Things?: Saints and Worshippers from the Martyrs to the Reformation

Robin Lane Fox, Pagans and Christians

Robert Finucane, Contested Canonizations: The Last Medieval Saints, 1482 - 1823

Peter Brown, The Cult of the Saints: Its Rise and Function in Latin Christianity