The Church in Crisis Series with Dr. Alan Fimister

The history of Christianity cannot be understood without understanding the Ecumenical Councils of the Catholic Church. For nearly two thousand years, these councils have defended the Catholic Faith, clarified doctrine, condemned heresy, reformed Church discipline, and guided the faithful through some of the greatest crises in history.

From the First Council of Nicaea in A.D. 325 to the Second Vatican Council (1962–1965), every Ecumenical Council addressed unique theological, political, and cultural challenges while preserving the Deposit of Faith entrusted to the Apostles.

In this comprehensive lecture series, Dr. Alan Fimister, Professor of Theology, guides viewers through every Ecumenical Council in chronological order. Each lecture examines the historical background, major personalities, doctrinal definitions, political context, and lasting legacy of the councils that shaped the Catholic Church and Western civilization.

Whether you are studying Catholic theology, Church history, apologetics, or simply seeking a deeper understanding of the Church’s past, this series provides a rich and accessible guide to one of the most fascinating subjects in Christian history.

What Is an Ecumenical Council?

An Ecumenical Council is a solemn gathering of the bishops of the Catholic Church, convened by the Pope, to address matters of doctrine, discipline, worship, and Church governance. Throughout history, these councils have served as extraordinary moments in which the Church responds to heresy, resolves disputes, reforms abuses, and clearly defines the Catholic Faith.

The decrees of Ecumenical Councils have given the Church some of her most important teachings, including:

• The doctrine of the Holy Trinity
• The divinity of Jesus Christ
• The two natures of Christ
• The canon of Sacred Scripture
• The seven Sacraments
• Papal authority
• Justification and grace
• The Holy Mass
• The relationship between faith and reason

These councils remain foundational to Catholic theology and continue to shape the life of the Church today.

Why the Ecumenical Councils Matter

The Ecumenical Councils are far more than historical events. Their decisions continue to influence every Catholic today.

The Nicene Creed, prayed every Sunday at Mass, originated from the Councils of Nicaea and Constantinople. The Council of Ephesus defended the title of Mary as the Mother of God. Chalcedon defined Christ’s divine and human natures. The Fourth Lateran Council clarified Eucharistic doctrine. The Council of Trent answered the Protestant Reformation and initiated sweeping reforms. Vatican I defined papal infallibility, while Vatican II addressed the Church’s relationship with the modern world.

Understanding these councils allows Catholics to appreciate how the Church has consistently preserved the Apostolic Faith through centuries of controversy, persecution, and cultural upheaval.

The Complete Church in Crisis Series

Part 1 — Jerusalem to Constantinople (A.D. 49–381)

Journey from the Council of Jerusalem in the Acts of the Apostles through the First Council of Nicaea (325) and the First Council of Constantinople (381). Learn how the early Church defended the divinity of Christ, condemned Arianism, and gave the Church the Nicene Creed.

Part 2 — Ephesus to Chalcedon (431–451)

Explore two of Christianity’s most influential councils as the Church proclaimed Mary as Theotokos (Mother of God) at Ephesus and defined Christ as one Divine Person possessing two complete natures at Chalcedon.

Part 3 — Second Council of Constantinople (553)

Discover how the Fifth Ecumenical Council defended the Council of Chalcedon, addressed the Three Chapters controversy, and strengthened Catholic Christology.

Part 4 — Third Council of Constantinople (680–681)

Learn why the Church condemned Monothelitism and proclaimed that Jesus Christ possesses both a divine will and a human will in perfect harmony.

Part 5 — Second Council of Nicaea (787)

The final council of the first millennium defended the veneration of sacred images and ended the Iconoclastic controversy while safeguarding authentic Catholic worship.

Part 6 — Fourth Council of Constantinople (869–870)

Examine the final Ecumenical Council recognized before the Great East–West Schism, including the Photian controversy and the growing tensions between Rome and Constantinople.

Part 7 — First Lateran Council (1123)

The first Ecumenical Council of the Western Church addressed the Investiture Controversy, reaffirmed papal authority, and introduced important reforms in clerical discipline.

Part 8 — The Second, Third & Fourth Lateran Councils (1139–1215)

Three great medieval councils that strengthened Church governance, combated heresy, promoted reform, and culminated in the Fourth Lateran Council’s landmark teaching on the Eucharist and Church discipline.

Part 9 — The First & Second Councils of Lyons (1245 & 1274)

Discover the medieval struggles between popes and emperors, the attempted reunion with the Eastern Churches, the Crusades, and major developments in papal governance.

Part 10 — Council of Vienne (1311–1312)

Learn about the suppression of the Knights Templar, the Avignon Papacy, doctrinal controversies, and the challenges facing the Church during the late Middle Ages.

Part 11 — Council of Constance (1414–1418)

The council that ended the Great Western Schism, restored unity to the Church, condemned Jan Hus, and elected Pope Martin V after decades of competing papal claimants.

Part 12 — Council of Florence (1431–1449)

One of history’s greatest attempts to reunite the Eastern and Western Churches, while addressing conciliarism, papal authority, and the looming fall of Constantinople.

Part 13 — Fifth Lateran Council (1512–1517)

The last Ecumenical Council before the Protestant Reformation sought to reform the Church but left many pressing issues unresolved on the eve of Martin Luther’s revolt.

Part 14 — Council of Trent (1545–1563)

The Catholic Church’s definitive response to the Protestant Reformation. Trent clarified Catholic teaching on Scripture, Tradition, justification, the sacraments, the Holy Mass, and instituted reforms that shaped Catholicism for centuries.

Part 15 — First Vatican Council (1869–1870)

Explore the definition of papal infallibility, the relationship between faith and reason, and the dramatic interruption of Vatican I during the Franco-Prussian War.

Part 16 — Second Vatican Council (1962–1965)

The concluding lecture examines the most recent Ecumenical Council, its historical background, principal documents, implementation, and continuing influence on the Catholic Church throughout the modern world.

Frequently Asked Questions

What is an Ecumenical Council?

An Ecumenical Council is a solemn gathering of the bishops of the Catholic Church, convened by the Pope, to define doctrine, settle theological disputes, reform Church discipline, and address important issues affecting the universal Church. The Catholic Church recognizes twenty-one Ecumenical Councils, beginning with the Council of Nicaea in A.D. 325 and ending with the Second Vatican Council (1962–1965).

Why are the Ecumenical Councils important?

The Ecumenical Councils preserved and clarified essential Catholic doctrines, including the Holy Trinity, the divinity of Jesus Christ, the canon of Scripture, the seven sacraments, the papacy, the Holy Mass, and many other foundational teachings. Without these councils, the history of Christianity would have unfolded very differently.

How many Ecumenical Councils has the Catholic Church held?

The Catholic Church recognizes 21 Ecumenical Councils:

• The first seven were held in the Christian East.
• The remaining fourteen were held in the West.
• The most recent was the Second Vatican Council (1962–1965).

What was the first Ecumenical Council?

The first Ecumenical Council was the First Council of Nicaea, convened by Emperor Constantine in A.D. 325. It condemned the Arian heresy, affirmed the divinity of Christ, and produced the Nicene Creed, which Catholics still profess at Mass today.

Which Ecumenical Council gave us the Nicene Creed?

The Nicene Creed was first formulated at the First Council of Nicaea (325) and expanded at the First Council of Constantinople (381). Together, these councils established the Creed that remains central to Catholic worship.

Which council declared Mary to be the Mother of God?

The Council of Ephesus (431) proclaimed the Blessed Virgin Mary as Theotokos, meaning “God-bearer” or “Mother of God.” This affirmed the unity of Christ’s divine and human natures in one divine Person.

Which council responded to the Protestant Reformation?

The Council of Trent (1545–1563) was the Catholic Church’s response to the Protestant Reformation. It reaffirmed Catholic teaching on Scripture, Sacred Tradition, justification, the sacraments, the Holy Mass, and implemented significant reforms in clergy formation and Church discipline.

What did the First Vatican Council define?

The First Vatican Council (1869–1870) defined the doctrine of papal infallibility when the Pope teaches ex cathedra on matters of faith or morals. It also issued the Dogmatic Constitution Dei Filius, defending the harmony of faith and reason.

Why is the Second Vatican Council discussed so often?

The Second Vatican Council (1962–1965) was the most recent Ecumenical Council and addressed the Church’s engagement with the modern world. Its documents, subsequent implementation, and interpretation continue to be widely studied and discussed by Catholics around the world.

Are all Ecumenical Councils equally important?

Every Ecumenical Council is authoritative, but some addressed issues with especially far-reaching consequences. Councils such as Nicaea, Chalcedon, Trent, Vatican I, and Vatican II have had particularly profound and lasting influence on Catholic doctrine, worship, and Church life.

Did every Ecumenical Council define new dogma?

No. Some councils solemnly defined doctrines in response to heresies, while others focused more on Church discipline, reform, governance, or pastoral concerns. Together, they preserve, clarify, and faithfully hand on the Deposit of Faith entrusted to the Church by Christ and the Apostles.

Why should Catholics study the Ecumenical Councils?

Studying the Ecumenical Councils helps Catholics understand how the Church has defended the truth throughout history. The councils explain why Catholics believe what they believe, how important doctrines were clarified, and how the Church responded to theological controversies and historical crises.

Where can I watch the complete Church in Crisis series?

This page contains every episode of The History of the Ecumenical Councils of the Catholic Church with Dr. Alan Fimister. Follow the series from the Council of Jerusalem to the Second Vatican Council and discover how each council shaped the life and doctrine of the Catholic Church.