Pentecost commemorates the descent of the Holy Spirit upon the apostles fifty days after Easter (Acts 2:1-41). The name derives from the Greek pentekostos, 'fiftieth,' referring to the Jewish festival of Shavuot (the Feast of Weeks), which falls fifty days after Passover. The typological connection is deliberate and profound: as the Law was given at Sinai fifty days after the Exodus, so the Spirit was given fifty days after the Resurrection, writing the law on human hearts rather than tablets of stone (cf. Jeremiah 31:33, 2 Corinthians 3:3). The Christian observance of Pentecost is among the oldest feasts after Easter itself. Tertullian (De Baptismo 19, c. 200 AD) mentions Pentecost as a season particularly appropriate for baptism, suggesting it was already a significant liturgical occasion by the early third century. The Council of Elvira (c. 305) references the Pentecost season. Eusebius (Vita Constantini 4.64) records that Constantine was baptized at Pentecost. By the fourth century, the feast was universally observed across both East and West. The BCP 2019 lists Pentecost among the seven Principal Feasts — the highest liturgical rank — and the Day of Pentecost is one of the four traditional Ember Day anchors, when prayers are offered for those called to Holy Orders.

Pentecost carries a distinctive liturgical character shaped by its dual identity as both the culmination of Easter and its own feast. The color is red — for the tongues of fire (Acts 2:3) and for the Spirit's presence in the Church. In the medieval West, the custom of releasing doves or dropping rose petals from church ceilings dramatized the Spirit's descent; the French name for Pentecost, Pâques des Roses, recalls this practice. The sequence hymn Veni Sancte Spiritus ('Come, Holy Spirit'), attributed to Stephen Langton (c. 1200), became one of the most beloved Pentecost texts in Western Christianity. In the East, Pentecost is closely linked with the feast of the Holy Trinity, which the Byzantine tradition celebrates on the same day (the West assigns Trinity to the following Sunday). The Kneeling Prayers of Pentecost Vespers in the Byzantine rite mark the formal end of the Paschal season: the congregation kneels for the first time since Easter. The BCP 2019 provides two collects — the first emphasizing the Spirit's revelation of 'the way of eternal life to every race and nation,' the second (from the 1549 BCP) asking for 'a right judgment in all things.' The Old Covenant overlay is significant: Shavuot celebrates both the wheat harvest and the giving of Torah, and the Pentecost narrative in Acts deliberately echoes Sinai imagery — the sound of wind, the appearance of fire, the gathering of nations.

Justin was born around 100 AD in Flavia Neapolis (modern Nablus, Palestine) to a pagan family and received a thorough education in Greek philosophy. In his youth he studied the Stoics, Peripatetics, Pythagoreans, and Platonists, seeking truth through philosophical inquiry. He became a Platonist, hoping to achieve direct knowledge of God through philosophy. Then, according to his own account in the Dialogue with Trypho, he encountered an old man who redirected him toward the prophets of Israel and toward Christianity. Justin investigated Christian teaching and became convinced that 'this philosophy alone is safe and profitable.'

Justin moved to Rome and established a school where he taught Christianity as the true philosophy. His apologetic method was distinctive: rather than dismissing pagan philosophy, he argued that the divine logos (reason) had scattered seeds of truth throughout human philosophy and ethics before becoming incarnate in Christ. Thus Plato, the Stoics, and other philosophers had participated in the divine logos — but only in fragmentary fashion. In Christ, the full expression of divine wisdom had appeared.

This framework, known as the logos doctrine or logos spermatikos ('seeds of the Word'), became one of the most influential ideas in Christian theology. It provided a way to integrate Greek philosophy into Christian thought and to argue that Christianity fulfilled rather than contradicted human reason.

Justin's surviving works include his First Apology (addressed to the Emperor Antoninus Pius around 155 AD) and Second Apology (addressed to the Roman Senate), along with his Dialogue with Trypho (a Jewish interlocutor), which is the longest early Christian document and a foundational text for Christian-Jewish polemic.

The Apologies remain invaluable sources for understanding 2nd-century Christian worship: they describe the Sunday gathering, the reading of the 'memoirs of the apostles' (Gospels), the homily, the prayers of intercession, the offering of bread and wine, the eucharistic prayer, the distribution to the present and to the absent (deacons bringing the elements to those in prison or unable to attend). Justin's account of the Eucharist — 'Not as common bread nor common drink do we receive these; but in like manner as Jesus Christ our Saviour, having been made flesh by the Word of God, had both flesh and blood for our salvation, so likewise have we been taught that the food which is blessed by the prayer of His word... is the flesh and blood of that Jesus who was made flesh' — articulates a high theology of the sacrament that would shape Christian eucharistic theology thereafter.

Justin was denounced as a Christian, tried before the Roman prefect, and beheaded around 165 AD. The Acts of Justin and his Companions, which records this trial and execution, survives as an authentic martyrdom account.

Traditionally, Justin is venerated as a saint and martyr who died defending the faith. Later hagiographic sources elaborate upon his life and teaching, but these expansions are minor compared to the full body of his own writings that have survived.