If every denomination is skeptical of every other denomination, why shouldn't non-Christian outside observers be skeptical of all denominations?

Question

To the best of my understanding, Christianity lacks a unified theory or epistemology. Instead, each denomination proposes its own framework (though calling these "theories" may be controversial; see here and here) that combines practical/experiential and non-practical/abstract elements. There are significant disagreements between denominations, each having its own epistemological basis—either explicitly defined or implicitly assumed—by which they often critique or reject the perspectives of others. To illustrate, here are some prominent examples:

• Jehovah's Witnesses receive skepticism from other denominations because of their rejection of the Trinity, unique eschatological beliefs, and exclusive claim to doctrinal truth.
• Latter-day Saints (Mormons) face skepticism for their additional scriptures like the Book of Mormon, beliefs in continuing revelation, and doctrines about God and the afterlife that differ from mainstream Christianity.
• Catholicism includes beliefs such as Marian apparitions and Eucharistic miracles, which other denominations often view skeptically as unbiblical or exaggerated.
• Pentecostals and Charismatics are critiqued for their emphasis on spiritual gifts like speaking in tongues, healing, and prophecy, which some see as lacking biblical or historical support.
• Calvinists hold strong views on predestination and the lack of human free will in salvation, which others find incompatible with notions of divine justice and human responsibility.
• Eastern Orthodox theology and practice differ from Western Christianity in areas like the Filioque controversy, the veneration of icons, and the concept of theosis, which others sometimes dismiss as overly mystical or traditionalist.

Suppose an outside, non-Christian observer sympathetic to Lakatos' concept of Scientific Research Programmes examines the landscape of deep Christian disagreements. Each Christian group is skeptical of every other group, with no shared research project advancing toward the truth—each simply holding its own beliefs regardless of what others believe. What reason does Christianity offer this skeptical observer not to doubt all denominations simultaneously? If there are N denominations, and each is already skeptical of the other N-1 denominations, why would it be unreasonable for a skeptical observer to extend this skepticism to all N? After all, it’s merely adding one more denomination to the list.

Alternatively, does Christianity present its own version of a progressive research programme (in line with Lakatos' definitions of progressive and degenerative programmes, as explained here)? Could such a programme offer a pathway for an outside observer to eventually converge on certain truths that might align with one denomination or another?

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Additional clarifications:

• If an answer merely focuses on listing a minimal set of Christian tenets as the theoretical hard core of Christianity (in Lakatosian terms), that would still leave unanswered why an outside skeptical observer would have any reason whatsoever to accept these hard core tenets in the first place in light of the fact that (1) even within Christianity there are smaller groups that do not accept them, and (2) a simple listing of tenets doesn't explain how these tenets are useful to make progress in our understanding of reality.
• Related to the previous point, it's important to keep in mind that a key concept that Lakatos retains from Popper is falsifiability, which means that a scientific research program has to make falsifiable predictions which are so in virtue of being testable empirically. Thus, does Christianity share this scientific appreciation for the empirical testability of its claims to any extent whatsoever?

Answer 1

This "frame challenge" answer may not be what you want, but I hope it's helpful to highlight the fundamental difference between "progress" in theology vs. "progress" in science vs. "progress" in knowing God. Theology prioritizes the "once given" revelation but science thrives on making "novel predictions". In theology, the progress is more unified understanding, and "prediction" / "new knowledge" is frowned upon. But in personal mystical relationship with God, yes, there is "progress" in knowing God more, assisted by greater revelation by God himself (grace of the Holy Spirit) to that individual. But theology to that individual serves merely as a "given" guide for the spiritual journey, rather than something that the individual can "improve" upon. Theology, as in science, is a communal enterprise.

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What reason does Christianity offer this skeptical observer not to doubt all denominations simultaneously?

Does the sun and the stars revolve around the earth, or does the earth revolves around the sun? Science finally answered the question, but notice how the conflicting theories didn't make a person skeptical of the existence, the goodness, and the beauty of the sun, the stars, and the earth.

So the reason that Christianity offers one to not doubt all denominations simultaneously is how they are all centered on the love of God who sends his "son" Jesus to "save" us and who eventually will make everything right at the end of time. Denominations may construe how Jesus is "son" differently, may offer different definitions of "save", and may offer different theories of the events leading to the final judgment. But all denominations teach the centrality of the love of God expressed in Jesus with whom we need to unite ourselves by whatever process a denomination prescribes that culminates in Jesus's Second Coming. Please notice how "uniting ourselves with Jesus" (a living Being) is very different than "intellectually adhering to a set of propositions about Jesus." Thus Jesus is the irreducible core of Christianity that no denominations contradicting one another can eliminate: the historical Jesus who truly died, truly resurrected, and who is now glorified "sitting at the right hand of the Father". Without Jesus who is now living, there is no sense in uniting ourselves with Him, and Christianity crumbles from the center.

Naturally we ask who is Jesus, what is His nature? Unfortunately here is where you need to make a choice between Jehovah Witnesses, Latter-day Saints, and mainstream Christianity. Even so, this is a disagreement about our understanding of Jesus, not about Jesus's loving us and making Himself available for us to be united with Him, which all denominations teach as absolutely true. If you're willing to narrow your choice to the 3 mainstream branches of Christianity, the commonality ("hard core tenets") will be more extensive, which is based on the Apostle's Creed and which you can find out from C.S. Lewis's description in Mere Christianity. To them the most important doctrine is Jesus is God (the sine qua non of Christianity), where "God" is understood in the Trinitarian way (Nicene creed) and "Jesus" is understood to be the Incarnation of the 2nd "Person" but who is also 100% human (Chalcedonian definition). It is supremely important for three reasons:

1. To preserve monotheism (Jesus is the human being of God, not a separate being)
2. Jesus has to be 100% human to save everything in our humanity ("That which is not assumed is not healed"). Jesus also has to be 100% human to be in solidarity with us in facing temptation, but victoriously. And thirdly, Jesus not only shed his glory to be a mere human made out of dust, but also placed himself in solidarity with those of lower socio-economic and cultural status.
3. Jesus has to be 100% divine to possess the source of the grace to forgive us, the power to restore our humanity, and eternal life.

Why would it be unreasonable for a skeptical observer to extend this skepticism to all N?

It's not unreasonable, so you can end up being an atheist, a Buddhist, or a Muslim.

But if you think it reasonable that to believe in Jesus is central to your ultimate happiness and to your life after death, the Jesus who forgives and "paid" for your wrongdoings (however they are defined and whatever "paid" means), the Jesus who is God's provision (i.e. the "Lamb of God who takes away the sins of the world"), then despite STILL being skeptical on which denomination has the whole truths about God, this rough idea about Jesus should STILL be good enough to lead you to the right path. In this way, total skepticism is overruled by TRUST in the God who loves us in Jesus.

But if you are skeptical toward the God who sent Jesus in the first place, to the point of not being able to say "yes" to accept the gift, it doesn't matter which denominations you are more skeptical towards, since denominations can only point you in the direction of God (according to their theology). The journey is yours alone. Saying "yes" is when you choose to ride a car or a plane even though you're still skeptical which car brand or which airline is the safest.

Why an outside skeptical observer would have any reason whatsoever to accept these hard core tenets in the first place ...?

Those tenets may not be falsifiable in the same way as in science (since part of the reality that theology deals with is historical and God is not subject to experimentation) but at least they become the basis for seeing the world in a new way which you CAN then "test". C.S. Lewis famously said what is written on his memorial stone in Westminster Abbey:

I believe in Christianity as I believe that the Sun has risen, not only because I see it but because by it I see everything else.

(conclusion of his 1944 paper Is Theology Poetry?)

No potential believer needs to understand the full theology of Jesus to take advantage of Jesus's promise to be the Light to you, just as no one needs to understand planetary movements to benefit from the sun. "Taste and see that the Lord is good; How happy is the person who takes refuge in him!" (Ps 34:8). Faith first, understanding follows. Unlike the Enlightenment prejudice, Christianity teaches that Faith is Rational (listen to the lecture The Light of Reason and the Light of Faith).

Thus, does Christianity share this scientific appreciation for the empirical testability of its claims to any extent whatsoever?

The first thing to be said is to understand what does it mean for theology to be a "science" which Aquinas defines (paraphrased by Fr. Thomas White) to mean "a study of the inner intelligibility of the mystery of God revealed in Christ through the Church." This covers a particular person's knowing the Trinitarian God and His Incarnation through the light of faith strengthened by the grace of the Holy Spirit, which is experiential. Theology understood in this way includes making progress in "knowing God" personally, rather than the modern study of theology which tends to be mostly cerebral. I refer you to the linked video above for a brief introduction of what "empirical testability" means in that context.

But for secondary doctrinal differences among denominations, which are many (just look at this list), the strategy usually has to do with proper interpretation of the Bible and choosing the controlling ideas from a denomination's theology that affect interpretation. I suggest you can make progress to discern a denomination's doctrine's "testability" by investigating it using Analytic Theology for better clarity over the terms used, and for discovering its inner coherence. Meaning, if after trying your best to see a doctrine's coherence there is STILL something that bothers your reason, then it fails your test.

Reading the latest systematic theology from a particular denomination helps too. After comparing various systematic theologies of different denominations and after engaging God in a prayerful manner, I think you can make progress to sense which denomination is "truer" for you.

Answer 2

Hilariously, you are liable to receive different answers from different denominations and theological schools.

With just a brief scan of Lakatos' programme I suggest that, to a very large degree (and with a few exceptions), this programme is exactly what is taking place:

A Lakatosian research programme is based on a hard core of theoretical assumptions that cannot be abandoned or altered without abandoning the programme altogether. More modest and specific theories that are formulated in order to explain evidence that threatens the "hard core" are termed auxiliary hypotheses. Auxiliary hypotheses are considered expendable by the adherents of the research programme—they may be altered or abandoned as empirical discoveries require in order to "protect" the "hard core".

In the case of historical and Biblical Christianity the "hard core" tenets that cannot be abandoned follow from two primary theological assumptions, 1) God is true, 2) The Bible is accurate. The tenets which proceed are as follows (these are broad brush stroke portraits):

1. There is one, and only one, eternal Being who is the creator and sustainer of all things.

2. That Being is revealed as Father by the eternally begotten Son in one Holy Spirit and each of these three is fully God: One What and three Who.

3. All mankind and each in particular have sinned and fallen short of God's glory and are, while physically "alive", spiritually dead; being separated from the only source of spiritual life - God Himself. This is not a problem that we can fix.

4. The eternal Son became flesh (Jesus the Christ) and died, was buried, and rose again the third day in order to reconcile us to the Father.

5. This reconciliation is all of God from first to last and involves all three "persons" of the Godhead. It is by God's grace that we have access to Him through faith in what God, in Christ, has done.

6. Christ is coming again to judge the living and the dead and establish an everlasting Kingdom

After this come the many 'orthodox' denominations who perceive and hold to "auxiliary hypothesis" and debate them, often vigorously. A few examples are the filioque controversy, continuationism vs. cessationism, Calvinism vs. Arminianism, and many more. This can become quite divisive if it is not remembered that these "auxiliary hypothesis" can not replace and must be sacrificed in favor of the "hard core" center.

Many denominations promote belief in certain "auxiliary hypotheses" as necessary for faithful membership in that denomination. That is agreeable within Lakatos' framework, I think. Tensions result when these auxiliaries are misunderstood or promoted as necessary for Christianity, as though they are part of the "hard core" (think Marian Dogmas or speaking in tongues, to name but a few).

There are many theologies which call themselves Christian and yet reject one or many of these "hard core" tenets. Some claim the existence of multiple Gods. Some claim that Jesus was merely a man. This can be confusing and lead to the conclusion that Christianity has no centerpiece but what has actually happened in those cases is that "auxiliary hypotheses" have been accepted to the exclusion of the "hard core" tenets. Here, Christianity has been both claimed and abandoned simultaneously.

The perceived lack of a unified theory, I suggest, comes from our human (sinful) proclivity to sacrifice keeping the main things the main things in favor of feeling accepted or intellectually satisfied within a man-made framework. In every denomination where the "hard core" tenets are protected in Lakotian fashion are found those for whom:

there is neither Greek nor Jew, circumcision nor uncircumcision, Barbarian, Scythian, bond nor free: but Christ is all, and in all. Colossians 3:11

This is the body of Christ worldwide ... Christ in you, the hope of glory. Everything else is mere religion with varying degrees of accuracy.

Answer 3

Yes, if denminations are sceptical of each other, it would probably be true that outsiders would also be sceptcal. But I am not convinced that all denominations are sceptical of each other. I do not believe Evangelicals are, as they have in their fold, members of many denominations.

But for argument's sake, if they are sceptical of each other, outsiders who have heard that they are, will not be blameless if they are sceptical too.

But (again), if the Christians in each denomination would uplift Christ and not major on their differences,there would be less suspicion. But if an outsider is concerned about it, they need to surrender to Christ so they don't receive the reward of their suspicion and rejection of Christ.

"He that believeth on him (Christ) is not condemned: but he that believeth not is condemned already, because he hath not believed in the name of the only begotten Son of God." John 3:18.

So it matters not what outsiders think of the church or of Christians, unless they surrender to Jesus, they will receive the reward of the lost -- which is the second death.

"Whosoever was not found written in the Book of Life was cast into the lake of fire." Revelation 20:15. (This is still future) (And hell fire is not everlasting, but as long as the judgment decides for each person)

The suspicious, sceptics, agnostics, atheists, hypocrites and unforgiven sinners must surrender to Jesus and put their ideas aside if they want to receive the reward of the rightous. This reward will be wonderful, as there will be no more tears, sorrow, pain, sickness or death. Revelation 20:4.

God will recreate this earth like it was in Eden, and all who love Jesus will inhabit it, for "the meek shall inherit the earth" -- for eternity. Matthew 5:5.

There will be no suspicion there.