Ascension Day commemorates Christ's bodily ascension into heaven forty days after the Resurrection (Acts 1:1-11, Luke 24:50-53). The feast always falls on a Thursday — forty days counted inclusively from Easter Sunday. The observance is ancient. Augustine of Hippo (Ep. 54 to Januarius, c. 400) already regarded the Ascension as a feast of apostolic origin, placing it alongside Easter and Pentecost as celebrations 'which the whole Church observes throughout the world.' Eusebius of Caesarea mentions it in the early fourth century. The Ascension stands as the christological complement to the Incarnation: at Christmas, God descends to take human nature; at the Ascension, human nature is taken up into the life of God. The theological implications are enormous — our flesh, our humanity, is now at the right hand of the Father. The BCP 2019 lists Ascension among the seven Principal Feasts, giving it the highest possible liturgical precedence. The ten days between Ascension and Pentecost have traditionally been kept as days of prayer and expectation, recalling the disciples' waiting in the upper room (Acts 1:12-14). Some Anglican and Roman churches transfer the observance to the following Sunday, though the BCP 2019 does not explicitly authorize this practice.

The Ascension has shaped both the liturgical calendar and Christian architecture. The tradition of extinguishing the Paschal Candle after the Gospel reading on Ascension Day — symbolizing Christ's departure from visible presence — was widespread in the medieval West, though modern practice varies. Egeria records a vigil service at the Imbomon (the traditional site of the Ascension on the Mount of Olives) in the 380s, and the feast was well established in both East and West by the fifth century. In the Byzantine tradition, the Ascension is one of the Twelve Great Feasts, and its icon — Christ ascending in a mandorla of glory while the apostles gaze upward and angels announce his return — is among the most theologically rich in the Eastern iconographic tradition. The two men in white (Acts 1:10-11) who promise Christ's return connect the Ascension forward to the Second Coming, making it both a feast of accomplished salvation and eschatological hope. The collect in the BCP 2019 focuses on the ascent of hearts and minds: 'May our hearts and minds also there ascend, and with him continually dwell.' The season between Ascension and Pentecost — sometimes called the 'Great Novena' — is a period of prayer for the coming of the Spirit.

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.