Atonement doctrine in the pre-Nicene Fathers
By far the strongest view of Jesus' saving work within the early Fathers is one that sees his primary work as being that of a teacher, who imparts to humanity information about how to live in a way that God considers righteous. His teachings and example are considered to be able to lead humans to live righteous lives in correct worship of God and correct behavior. The church movement is seen as continuing and disseminating these teachings, and thus the founding of the church is considered an important part of Jesus' actions.
This concept of Jesus as a teacher of righteousness is universally a primary soteriological concept in the pre-Nicene Fathers. In the large majority of them, it is the only one. Protestant scholars have historically had a tendency to label the Christianity of this period, somewhat derogatorily, as "Moralism" due to the emphasis placed on moral effort in salvation. (Judgment by Works + Free Will + Christ as Teacher = "Moralism") This "Moralism" is the theology of the Apostolic Fathers and the Apologists which constitutes the orthodoxy of the second century AD (see here).
Some of the later pre-Nicene Fathers developed other ideas of Jesus' saving work in addition to holding the one described above. As I outlined in my previous post Greek philosophical concepts about union with and contemplation of the divine began to influence Christian thought. In the last quarter of the second century the thinking of Irenaeus of Lyons and Clement of Alexandria was heavily shaped by these ideas. In their writings the notion of Christ as a teacher and example of moral righteousness remains of first importance, but alongside it and of equal importance is the attainment of the human soul's unity with God through mingling with the divine. This conception occurs to a much lesser extent in a many of the subsequent pre-Nicene writers (eg Origen, Hippolytus, and Methodius) but climaxes again at the close of the pre-Nicene period in the writings of Athanasius and was extremely influential thereafter and the main driving force in the Christological councils of the fourth to sixth centuries.
Another view of Jesus' work that makes its first appearance in this period is the concept of "Ransom from Satan" / "Christus Victor" which appears in the work of Origen in the early third century AD. This idea sees sinners as falling under the power and influence of Satan and needing to be freed from Satan through payment or force. Origen in his biblical commentaries often depicts a major part of Jesus' work as being a payment to Satan to free us from his grasp (although the concept of Jesus as a teacher of moral virtue receives more emphasis). This view of rescue from Satan does not seem to have caught on during the pre-Nicene period, but its popularity seems to have blossomed during the fourth century - being popularized by Gregory of Nyssa and by a resurgence of interest in the writings of Origen.
At the close of the pre-Nicene period in the early years of the fourth century AD, two contrasting Christian writers best depict the difference between the past and the future. Lactantius wrote a systematic theology of Christianity in which the "Moralism" typical of the pre-Nicene period is in fullest flower, and which represents the close of an era in the sense that it is really the last major work in which the concept of Christ-as-Teacher stands alone. Meanwhile Athanasius was authoring a work in which took further than ever before the concept of a union with God through the God-man Jesus, and which also suggested the idea that Jesus suffered punishment from God on our behalf... both ideas were signs of things to come.