What do you think needs to happen, in order for the Church to combine back to its original form and rid the Christian Church of all its schisms and heresies?
As soon as people started to think critically about Christ, Christians have differed. The idea that at the beginning there was one, unbroken church with no “heresies” is a myth**.** People believed and taught many things at the beginning: Adoptionism, Docetism, Montanism, Marcionism, different forms of Gnosticism, and Ebionism - just to name a few. You might say that early Christianity was far more diverse than our modern Christianity. Most Christians (with, perhaps, the exception of Jehova’s Witnesses and the LDS) have the exact same view of Christ’s divinity, the Trinity, the New Testament cannon, angels and demons, Christ’s teachings and thier effect on a Christian’s interpretation of Jewish tradition, among many other things. When it comes down to basics, the vast majority of Christians today agree on much more than the Christians of the first, second, third, and fourth century.
Furthermore, it should be noted that many of our Catholic beliefs were developed slowly over time. The exact defination of the Trinity, for instance, was a developed idea - partially forged out of a number of differing “heretical” beliefs. Even the specifics of the nature of Christ were slowly defined over the years.
Personally, I think this question could probably be re-phrased into “how can we convert everyone to Catholicism?” I suppose that’s a perfectly valid question for a true believer of Catholicism, but I might point out a contradiction in Church teaching on the subject. Take a look at the Vatican 2 documents Nostre Aetate and Lumen Gentium. We are to respect and appreciate othere religions. Personally, I don’t think converting all of Christianity to Catholicism is going to happen. Furthermore, I don’t really think that it should be a priority. There’s value to our differences, as the Bishops in Nostre Aetate point out. Having a multitude of religions is a good thing. We ought to learn to live with eachother, accept our differences, and work towards eliminating the real evils in our world (poverty? war?).