I first argued that the atoning death of Jesus on the Roman cross (together with the Incarnation that made it possible and the Resurrection that made it worthwhile) is the central event of all church history. Though Christ-followers today have disagreements about the number of sacraments they celebrate, and the details and frequency of those sacraments, all believers worldwide partake of communion and have been doing so ever since the resurrected Jesus ascended.
But more than that, we can see that the Cross is also the most decisive event in all of human history. Not only do we who came after it look back upon it, but for more than a millenium and a half the people of God (the Israelites) looked forward to it. They did this whenever they celebrated the Passover, which was a type of the Messiah's lamb-like offering (Isaiah 53:7). They also did this whenever they offered atoning sacrifices for their corporate and individual sins. Such sacrifices did not of themselves forgive sins, but acknowledged Messiah's future, once-for-all sacrifice (Hebrews 10:10) that would effectively deal with humanity's ultimate problem--separation from our Creator due to our sin and rebellion.
But even to say that the Cross is the focal point of all human history is to understate the case. The fact is that Christ's redeeming act of obedience on the Cross transcends cosmic history, and that both as to eternity future and eternity past. Revelation 5 contains a vision of Heaven, of a time and place outside of our universe. And even there, we (in our own glorified, resurrected bodies) and the angels will be focussing on the Cross and crying "Worthy is the Lamb who was slain!" And we are told (in several Scripture passages, including Titus 1:2 and Ephesians 1:4) that our redemption in Christ was promised before the creation of the universe. II Timothy 1:9 says that God
saved us and called us to a holy calling, not because of our works but because of his own purpose and grace, which he gave us in Christ Jesus before the ages began.The Greek here means "before times eternal."
Throughout this discussion of the Cross, I used words like 'central,' 'decisive,' 'important,' and 'critical.' But there were a couple of words I didn't use, and that for good reason. In stressing the centrality or importance of a particular moment or event, we sometimes use the words 'crux' or 'crucial.' Crux means 'a pivotal or essential point requiring resolution or resolving an outcome.' Crucial means 'important or essential as decisive or as resolving a crisis.' (Again, the crisis resolved by the Crucifixion is our eternal separation from God by our own sinfulness.) But had I referred to the Crucifixion as the crux of human history or the crucial moment in cosmic history, I would have been guilty of redundancy. That's because both of these words have as their root the Latin word meaning 'cross' or 'torture.'
In short, whenever we employ the words 'crucial' or 'crux,' we are tacitly acknowledging that the standard of centrality, importance, and decisiveness against which all other things must be measured is the substitutionary death upon a Roman cross of the eternal Son of God outside Jerusalem in AD 30.