What is a "Doctor of the Church?"

On January 24 (yesterday) each year, the Catholic Church celebrates the Feast of St. Francis de Sales.  As I read a little about his life yesterday, I became aware that he has been declared a “Doctor of the Church.”  While I was aware that some Catholic saints have this title, yesterday’s feast got me thinking about them.  What is it that makes a saint a “Doctor of the Church?”  How many saints have been declared “Doctors?”  Who are they?  What are some of their qualifications and accomplishments?

I found a concise definition of “Doctor of the Church” in the book The Essential Catholic Handbook, a publication of the Redemptorist religious community.  The definition is this:  “An ecclesiastical writer of eminent learning and outstanding holiness because of his/her contribution to the explanation and defense of Catholic doctrine.”   So, what makes a saint a Doctor of the Church and what are the qualifications?  The saint must be a writer who has demonstrated superior learning as well as outstanding holiness and must have contributed majorly to interpreting and defending Catholic doctrine.  How many saints have been thus declared?  There are currently thirty-four Doctors of the Church, the most recent being St. Gregory of Narek who was thus declared by Pope Francis in 2015.  All have been declared doctors by popes

Some on the list are easily recognizable to Catholics and non-Catholic alike, including St. Augustine, St. Thomas Aquinas, and St. Therese of Lisieux.  Others lived around the time of the Protestant Reformation and were known for defending Catholic doctrine in the face of the reformation movement.  These include our St. Francis de Sales as well as St. Teresa of Avila, St. Robert Bellarmine, and several others.

St. Therese of Lisieux is an especially interesting example.  She is best known for writing her autobiography The Story of a Soul.  In it, she describes what has come to be known as “The Little Way,” which is a way to holiness for those who live a life of poverty and who serve God through love and through small and simple means.  It has been recognized as a great work for people who are not known for their accomplishments or greatness but for their love of God and simple acts of obedience and love.  It turned out that her “little way”, despite the implication of its title, was recognized as a “great way” for anyone, even the smallest among us, to reach the highest level of sanctity.  It was recognized as a work that demonstrates her outstanding contribution to Catholic doctrine by Pope St. John Paul II in 1997.