Piper rejects the analogy. The sinfulness of homosexuality is non-negotiable. Differences over baptism are another matter. As a Catholic reading this debate, what strikes me is the incoherence of Piper’s hermeneutical objection. On what grounds does Piper single out one set of doctrines (sacramental theology) as negotiable and another (human sexuality) as non-negotiable? As a Catholic, I see this whole way of framing the issue as misguided. Protestantism has never been able to provide a consistent account of the distinction between “essential and non-essential.”He goes on to give a number of examples from the history of Calvinism that show inconsistencies in what doctrines are deemed essential. He really does his homework. He is a professional historian who left Calvinism for Catholicism because the history of the church and Calvinism in particular raised so many questions.
This is a classic problem with protestantism that seems like it should not be that big but ends up being huge. The problem that true Christians are supposed to agree on essential doctrines and they just don't. So you have two ways to go. You can declare that the group that disagrees with you are not true Christians or you can declare that the doctrine in question is non-essential.
Why is that? Because protestants all claim their doctrines are bible based. If someone makes an error then the problem is either with the person or with the bible. Either the bible is not clear enough or the person is in disobedience. If the doctrine is important you can't say the bible is unclear on it. That would violate Sola Scriptura. So you have to say the person has made a very serious error.
In former times protestants were OK with saying other protestants and certainly Catholics were in serious error and often declared them to be going to hell. Modern protestants don't like to do that. The amount of personal interaction between any two protestant groups of any size makes that a hard sell. When you know someone even just online they become a lot harder to dismiss as not serious Christians. So the tendency among protestants is to avoid declaring any issue to be essential.
The trouble is that at least conservative protestants know that is not true. Certainly there are many beliefs they don't want to make optional within their particular church. Yet if it is non-essential then how can you discipline a pastor even within the denomination over it? Yet there are limits. Everyone has a limit where they feel someone has now left the faith. Where to draw the line. More importantly is how to draw the line. What is the process? Is it denominational? Is it interdenominational?
Back to Dr Anders:
The Catholic Church clearly teaches the immorality of homosexual unions, but it also clearly defines the necessity of baptism, the structure of Church government, the nature of the Eucharist, and so forth. This is not to say that Catholics regard all doctrines in exactly the same way. We acknowledge a “hierarchy of truths,” in which some doctrines are closer than others to the foundations of our faith. But that doesn’t make subordinate doctrines either unimportant or optional. The reason for Catholic clarity is the existence of a living Magisterium, the patrimony of tradition, and the dictates of natural law.I actually think he made a small error here. Catholicism can define essentials doctrines. They have defined a lot more of them than Protestants are used to. That does not make them all essential. Some are actually optional. It is just that the church has received much in the way of revelation and can make that clear in her teachings. Doctrine is a source of unity rather than a source of division.
What if someone disagrees with the church on a matter of defined doctrine? It is really their problem. It does not create this atmosphere of uncertainty around the issue. The church's teaching remains clear. Still there is no need to overstate the error the person has made. We can imagine that something that is clear to most people might not be clear to everyone. Many have a faulty understanding of church authority so they can arrive at erroneous doctrines by making honest mistakes. We don't need to assume there is a much more serious spiritual problem.