Q. What is the criterion used to determine if one qualifies to become a saint? What is the origin of those criteria?
A. Here’s a reply from Father Reginald Martin:
The Catholic Encyclopedia states, “Canonization is an act … by which the pope decrees that a … member of the Catholic Church … be inscribed in the book of the saints (Vol. 3, p. 55). However, this is the modern custom; in the Church’s early history, saints were acknowledged by the local community. Originally, martyrdom earned an individual the honor of sainthood. By the 10tth century, this was expanded to embrace a life of exemplary holiness or charity.
Because reputations were often exaggerated, the local bishop eventually became the authority who pronounced a person a saint. Pope Gregory IX (r. 1227-41) established norms for investigating the holiness of a person’s life, and thenceforth the pope determined who deserved to be honored as a saint.
Today, if someone dies leaving a personal legacy of exceptional Christian life and service — especially if she or he appears to be a particularly effective intercessor before God — a bishop may begin interviewing those who knew the individual. This testimony is sent to the Holy See’s Congregation for the Causes of Saints, which advises the pope whether to continue. If miracles can be adduced, the individual may be declared a blessed. If an additional miracle can be proven, after being beatified, the person may be declared a saint.