The title Apostolic Fathers is given to people who in their lifetime knew the Apostles of Jesus Christ. Hence the importance and soundness of their doctrine lie in the fact that it can be directly linked to the teaching of the Apostles themselves. Through their writings we get a first hand picture of the situation and of the problems of the Church at the turn of the first Century (that is, more or less between then years 80 and 150) of the Common Era.

Saint Justin (b. 100 AD) is considered the most important apologist of the 2nd century. At that time, in the Roman Empire, Christians were arbitrarily sentenced to death for the simple fact of being Christians, even if innocent. Therefore, around 150 AD, he submitted to the Roman administration two “Apologies” (petitions) in favor of Christians. However, around 165 he also was beheaded for being a Christian.
Among the main subjects of his research is the Word of God Who even before becoming a man was present as a seed in the hearts of all men and taught them to act according to reason. And such Word marks the whole world with Christ's symbol of victory, the cross. All his ideas greatly influnced later Christian writers.

The Muratorian Canon (also known as Muratorian Fragment) is the oldest known list of New Testament books.
It was probably written around the year 170, but it was discovered by Ludovico Antonio Muratori and published by him in 1740.

This small work by Irenaeus, probably written around 190, is often and rightly referred to as an 'Ancient catechism for adults'.
In fact, the issues addressed are aimed at detecting the continuity between the Old and New Testaments and their meeting in the figure of the Word of God, Son of God and Son of Abraham.

These four booklets of Tertullian were written between 197-201. As one among the first great Christian apologists, Tertullian, already at that time, gained a reputation that is still acknowledged today.
In fact, at that time, not only in the pagan Roman Empire, but even in the Church itself, many heretical movements and writings circulated.
In such a chaotic situation, he argues that only the faith and doctrine of the catholic Church are reliable and trustworthy, because that Church received that faith and that doctrine directly from the Apostles, who had received them from Christ himself.

“On Prayer” and “Exhortation to martyrdom” (written between 233 and 235) are among the most popular works of Origen.
∙ “On Prayer”: Origen first of all states that in the Christian life prayer is a dialogue with God aimed at lifting up the soul to Him. Then he explains the “Our Father” in such a way that even today's people cannot help but be amazed in front of his inspiring spirituality.
∙ “Exhortation to martyrdom”: In 235, when the Roman Empire began to persecute Christians, Origen wrote this small book in order to encourage Christians arrested during persecution to willingly give up their lives in order to bear witness to Christian faith. For there is no more glorious death for a Christian than death as a martyr.

The commentary of St. Cyprian to the Lord’s prayer has been a Christian ‘classic’ from the time it was written, in the year 251.
In this book, the bishop of Carthage (North Africa), besides commenting on the text of the prayer itself, several times highlights the ideas that, as a pastor, are his main concern: unity of the Church and concord among the faithful.

While the ‘Contra Gentes’and ‘De Incarnatione’ were written for a pagan audience and are still regarded classics of theology, the ‘Life of Antony’, written for monks both in Egypt and abroad, is Saint Athanasius’ most loved writing, read by all christians for inspiration.
These four books were written more or less between the year 335 and the year 360.

The most famous work of Saint Cyril is the 24 sermons which were delivered in the Basilica of Holy Sepulchre in Jerusalem in 346 or 359 AD. They are known as “Catechetical Lectures” or “Catechetical Lectures of Jerusalem.”
The first 18 sermons are aimed only to the catechumens, and were given in preparation for Easter; while the remaining 5, delivered the week after Easter, target the newly baptized, and focus on the three sacraments of Christian Initiation, i.e. Baptism, Confirmation and Eucharist, and for this reason are called “Mystagogic Catechesis”.

The Sacramental catechesis (De Mysteriis) of Saint Ambrose is one of the ‘classic’ texts dealing with Christian initiation: the renown Bishop of Milan explains to the newly baptized the profound meaning of Baptism, Confirmation and Eucharist.
It was probably written about A.D. 387.

The Commentary on the Apostles’ Creed (Commentarius in Symbolum Apostolorum) is Rufinus’ most important work, aimed at persons under instruction for the sacraments.
While it is a word by word guide to explaining the Creed, it also offers a glimpse of how, in the course of time, the Creed developed from its ancient form in order to face heresies threatening Christian faith. For this reason, in the Introduction to the book, four ancient Creeds are shown in their original Greek and Latin languages.
It was written about A.D. 404.

This sermon (On Shepherds) of Saint Augustin (written after the year 414) on the basis of a prophecy of Ezekiel, shows that as at the prophet's time, today too in the Church there are good and bad shepherds; bad shepherds being church leaders who do not care for the flock and pursue their own selfish interests instead of pursuing the interests of Christ.
The sermon deals also with a heresy of that time that threatened to disrupt the unity of the Church.

This sermon of Saint Leo the Great on the important passage of the Gospel of Matthew (Mt 5:1-5) is considered of great importance among similar sermons of other writers. In the sermon Jesus is shown as the new Moses who from the top of the mountain proclaims the New Law of the New Covenant.
Commenting the first beatitude (How blessed are the poor in spirit) Saint Leo explains that is not so much material poverty as spiritual poverty (that is humility) that makes man ‘blessed’.
The sermon was probably written in the year 449.

Since the early centuries, in the Church the conviction grew stronger and stronger that Mary, at the end of her earthly life, was assumed to heavenly glory in body and soul.
From a historical point of view, writings on this subject began to be written in various regions in the third century. They were usually called “Transitus of Mary”. Each of them, in addition to the main theme (Mary assumed to heavenly glory in body and soul), includes various imaginary sub-themes that evoke words, characters and events from the New Testament.
But even among all such characters and symbologies the main theme of the writings stands out clearly: Mary was assumed to heavenly glory in body and soul.
The original Syriac ‘Transitus’ from which in later times Transitus R and manuscript Augiensis were translated into Greek and Latin might have been composed in the fifth (or perhaps even in the fourth) century.

The famous text of the 6th Century (AD 516) that founded not only the spirituality, but also the culture of the Christian West.

Saint Benedict (480-547) is considered one of the main monastic figures of the Christian West.
His life written by Pope Gregory the Great between the years 593 and 594, was and is still viewed as a classic of Christian spirituality.