Clarity about the content of Christian beliefs has been a significant concern since at least the late first century C.E. Within a few generations after the death of Jesus, Christians had begun to debate doctrinal issues that went beyond the questions of ritual and practice that had preoccupied the earliest Christians. Emphasis shifted from the traditional Judaic orthopraxy to the gradual articulation of an increasingly distinctive body of Christian teaching about God, Jesus, and the ongoing divine presence called the Holy Spirit. Specific issues in the first of these categories included the concept of the Trinity and the relationship between divine grace and human initiative.

Christian teaching about Jesus sought to express the perfect blend of divinity and humanity in Christ and to understand how Christ is present in the sacrament or mystery called the Eucharist (where blessed bread and wine are partaken as a way of receiving Jesus). Doctrine concerning the Holy Spirit evoked questions as to the nature of revelation and of membership in the Christian community. The more these and other issues generated an increasing variety of views through the second and third centuries, the greater the need to set clear standards as to which were acceptable and which were potentially destructive. Beginning with the Council of Nicea in 325 C.E., mainstream Christian doctrine would take the shape of formal dogmatic expression. And since not all Christians would concur on a given formulation, differences of opinion on dogma would soon come to distinguish various churches from each other.