What was the most frequently asked question during the heretical controversies of the 4th century? Is this question still relevant today? How so? What does the bible say?
The church found it just as hard to nail down Jesus as the Romans did, as the issue of exactly who Jesus is (Christology) refused to die and rose up time and time again.
By the 5th Century, orthodox biblical doctrine had battled the Christological heresies of Doceticism (Christ isn't human), Adoptionism (Christ isn't God), Modalism (one God in three "guises"), Arianism (Christ as created being; therefore, not God), and Apollinarianism (non-integrated Christ). The obsession with this question persisted since it dictated how Jesus saves (Soteriology), and produced heresies like Pelagianism (humanity as independent/free from original sin and free from need for divine aid).
The Council of Chalcedon's (451AD) attempt to once again settle the question of who Jesus is once and for all proved inadequate since the issue has survived two millennium. Outside orthodox biblical doctrine, forms of Adoptionism and Arianism thrive among Unitarians, Jehovah's Witnesses, and Mormons, and Modalism reemerged within Oneness Pentecostalism. Even within orthodox Christianity, heretical views of Christ are often held by the naïve when sound theological teaching is lacking, and is impacting how we respond to Christ's saving grace.
Many modern church-goers offer lip-service to Chalcedon's results; their inaction reveals a Neo-Pelagianism has crept into the church. On the surface, John 14:7's clarity that those who know Jesus know the Father is accepted, but the preceding verse that Jesus is the only way to salvation is pragmatically ignored. Jesus is largely treated as a paragon moral teacher and the communal effects of sin are individualized creating a “will worship” that condemns those dying for grace. By extension, though contrary to Romans 10:14-16, the responsibility of salvation for unreached people falls on themselves, but God might mysteriously save them outside of Christ.
Recognizing the biblical doctrine of Christ as fully God and fully man is critical to the gospel. The correct response assures our salvation, but also demands reverent loyalty to our Lord's commands, especially Christ's Great Commission to reach the nations in Matthew 28:20.
Note: I recognize that there are (sadly) many additional misinformed views of Christ as identified by the Church, but these listed here are the predominant ones prior to the 5th century.