The earliest third order or tertiary dates back to the twelfth century, when many devout Christians were zealously moved by the Holy Spirit to radically reform Christendom by preaching. Some of these Christians gradually organized themselves into distinct groups, such as the Waldensians and the Humiliati. However, with much sincerity, but without teaching or oversight, their sermons and doctrine deteriorated into outright heresy, which forced the Church to restrict their preaching activities. This led many of them to become priests. Others were gathered into a cloister and took up religious life. And others remained outside, living a rule of life within the world, yet spiritually dependent on the one of the priestly orders and now for the first time in history called a Third Order or Tertiary.

In the early 1200′s, Saint Dominic was a priest who radiated a life of simplicity, purity, and love for God that resonated with such fervor that people wondered if Christ had been born again. At this time, he happened to be assigned the direction of a community of nine Catholic women in Prouille who had separated from the Albegensians.* He cared for their earthly needs and directed their spiritual formation and formed them into a community of nuns, who were the first church-sanctioned Dominicans. In a short time, a large body of laity who were living a life of piety found themselves attracted to St. Dominic and grouped themselves around his rising Order of Preachers and, constituted on their own, a “third order.” The priests were referred to as the first order, and the cloistered nuns, the second order. But throughout their history, third order Dominicans shared, with the first and second, in the same spirituality, the same superiors, and even aspects of the same habit such as the scapular.

From the fifteenth century on, the third order of Dominicans consists of men or women and can be divided into two categories, regulars and seculars. Regulars live in community, wear the habit externally, and take a vow to live according to the Dominican Rule. Seculars, whether married or single, cleric or lay, live in the world but privately follow the Dominican Rule, pray part of the Divine Office, wear some symbol of the Dominican habit, and make a solemn promise to live according to the Dominican Rule adapted to their life as Lay Dominicans.