Firstly, the argument for pluralism is I think ill-founded. Firstly, I think the game is given away the minute you have to try and say that should get special treatment which Groucho Marx does not receive. The minute this happens we enter the territory of special pleading, the only justification for which is that you personally happen to hold this particular god-man of antiquity to be your own subject of worship, while discounting every other of the hundreds of similar figures.
Secondly, your standards show the distinction between how theologians think and how historians think. When you make statements such as "I’m happy to suspend my most extremely skeptical questions about their existence [Jane Austen, Groucho Max, etc.]; why should I hold the historical Jesus to higher standards than this? Instead, historians seek to assess questions of 'plausibility' and 'probability' when it comes to the historical Jesus," this gives the game away. There is no reason to doubt or raise serious doubts about Groucho Marx because the evidence for him is infinitely times better than anything which exists for Jesus. There is no comparison, and to draw the comparison is to ignore the very different quality of evidence we have for them. It is clear from this outset you are approaching this not as a historian but as a theologian, which necessitates lowering standards, instead of maintaining them.
You ask "If historians are seeking plausibility rather than certainty with regards to the historical Jesus, then we might ask: what makes something more plausible than not? How should we measure plausibility?" The answer is the degree to which it conforms to observable, testable, and certain reality. Science has produced clear and concise knowledge of what is real and what is not. Every time you take medicine, every time you drive a car over a bridge, every time you type on your computer or phone, every time you watch TV, you inherently trust without even thinking the very practical and constructive knowledge and objectivity of science. Your every day life confirms what you know to be true by how you practice it. As Engels once said, "the proof of the pudding is in the eating." Simply put, practice proves what is real and there is no reason to doubt it. No one actually believes your argument. In practice, I don't think you do either.
Because I know for a fact that no legitimate, bonafide, non-sellout scholar would ever espouse ancient aliens crankery or Holocaust denial. And they would rightfully and correctly note that both positions are objectively rooted in racism, they would show all the evidence they are wrong, etc. And if you were contracted to debunk them and show why one of those are wrong, something tells me that you would not be pulling some theological stunt of going "everyone determines their own plausibility" (which is essentially your argument here), but would be showing all the reasons why these positions are objectively and declaring that authoritatively (I hope you would). You are welcome to prove me wrong, but frankly the one and only way to show that anything is incorrect is that there must be an objective metric by which we judge what is true and what is false. Otherwise is is just a hodge podge of personal opinions (at which point no one should take any of us seriously, as we have made ourselves a joke of standardlessness). The minute we get down to there being an objective reality which we can make authoritative knowledge claims about, we fundamentally therefore arrive at there being correct metaphysical and historiographical positions, and incorrect ones. And if the continued and constant, every day success of science is anything to go by, we know which one is correct.
Thus, the same metric you would use to disprove ancient aliens, is the same metric by which I discount all other non-secular "historiographies" and also various conspiracy theories and the likes.
Now I agree with you that there is no way we as humans can be totally objective, and unbiased. But it is simultaneously true that some of our theories and hypotheses are more objective and true than others. (And if you say ancient aliens theorists, Holocaust deniers, antivaxxers, or any other conspiracy theory is wrong, then you too agree with this statement that there are some positions more objectively true than others.) Which means the tests to be done are in evaluating which theories best correspond to reality by producing consistent and repeatable results. Theology and "Christian historiography" do not end up satisfying this criterion.
Your ending dilemma is also not one. You say:
"The alternative to this is either 1) the imposition of one specific set of theological and philosophical beliefs upon anyone wishing to approach to historical Jesus, as requirement for entry into the discussion, or 2) the construction of a comprehensive argument that demonstrates the superiority of one specific set of theological and philosophical beliefs over all others. The former is undesirable, as it is little more than arbitrary academic gatekeeping; and I don’t think the latter is possible (although I am happy to be proven wrong!)."
Firstly, all of us already construct arguments to demonstrate specific belief systems over others (2). Again, the ancient aliens and Holocaust denial examples are case in points. Serious people don't believe those things, and those who do believe them should not be taken seriously as intellectuals or thinkers. In fact, I don't think you or I would clutch pearls to see an academic espousing those positions removed from their teaching post. (I sincerely hope you wouldn't.) Hence, we also are fine with utilizing variations of (1). Hence, my position: we go with the framework which has produced the most consistent results. And that happens to be secular historiography and it isn't even close by comparison. Not only have secular historiographical methods led to proveable and working reconstructions of the past, but simultaneously the work done has allowed us to even have practical applications like predicting where to find archaeological sites, how to best dig them up, how to contextualize and date papyri, how to better understand ancient languages, etc. The orders of magnitude of gains in secular historiography are too many to count. Meanwhile, doing Christian historiography with a spade in one hand and a bible in the other has a long history of producing extremely dangerous, problematic, false, and often fraudulent results.
Lastly, I will also just add Occam's Razor to the mix. My view comports with known reality and doesn't require anything else. Theological ones require we add a bunch of extra religious and deity stuff none of which has been actually even demonstrated to be a part of reality. Don't multiply objects beyond necessity. Secular historiography produces better and more consistent results, which comport to reality, and does so without the added baggage theological "historiography." Thus, there is no comparison. One is simply better and more efficient.
I don't see much advantage to conversations like these in the end. Accepting your position, we cannot even rationally reason about history or its relation to reality. It is just a jumbled mess of random opinions all with no better footing than the other. This kind of "plurality" is not actually adding anything. There is also simply nothing wrong with methodological authority. In fact, we all already agree it is a good thing. If you are suffering a heart attack and your doctor says, "Well we have to burn sage to cure your miasma and then your heart will be fine," then I think we could all agree that doctor is a quack who should lose their license. Standards and gatekeeping are good actually. And I think it is high time biblical studies got better at both. This postmodernist theologizing is simply a bit bewildering and bewuthering to me. In the end, no one is a postmodernist on the surgeon's table.
Firstly, the argument for pluralism is I think ill-founded. Firstly, I think the game is given away the minute you have to try and say that should get special treatment which Groucho Marx does not receive. The minute this happens we enter the territory of special pleading, the only justification for which is that you personally happen to hold this particular god-man of antiquity to be your own subject of worship, while discounting every other of the hundreds of similar figures.
Secondly, your standards show the distinction between how theologians think and how historians think. When you make statements such as "I’m happy to suspend my most extremely skeptical questions about their existence [Jane Austen, Groucho Max, etc.]; why should I hold the historical Jesus to higher standards than this? Instead, historians seek to assess questions of 'plausibility' and 'probability' when it comes to the historical Jesus," this gives the game away. There is no reason to doubt or raise serious doubts about Groucho Marx because the evidence for him is infinitely times better than anything which exists for Jesus. There is no comparison, and to draw the comparison is to ignore the very different quality of evidence we have for them. It is clear from this outset you are approaching this not as a historian but as a theologian, which necessitates lowering standards, instead of maintaining them.
You ask "If historians are seeking plausibility rather than certainty with regards to the historical Jesus, then we might ask: what makes something more plausible than not? How should we measure plausibility?" The answer is the degree to which it conforms to observable, testable, and certain reality. Science has produced clear and concise knowledge of what is real and what is not. Every time you take medicine, every time you drive a car over a bridge, every time you type on your computer or phone, every time you watch TV, you inherently trust without even thinking the very practical and constructive knowledge and objectivity of science. Your every day life confirms what you know to be true by how you practice it. As Engels once said, "the proof of the pudding is in the eating." Simply put, practice proves what is real and there is no reason to doubt it. No one actually believes your argument. In practice, I don't think you do either.
Because I know for a fact that no legitimate, bonafide, non-sellout scholar would ever espouse ancient aliens crankery or Holocaust denial. And they would rightfully and correctly note that both positions are objectively rooted in racism, they would show all the evidence they are wrong, etc. And if you were contracted to debunk them and show why one of those are wrong, something tells me that you would not be pulling some theological stunt of going "everyone determines their own plausibility" (which is essentially your argument here), but would be showing all the reasons why these positions are objectively and declaring that authoritatively (I hope you would). You are welcome to prove me wrong, but frankly the one and only way to show that anything is incorrect is that there must be an objective metric by which we judge what is true and what is false. Otherwise is is just a hodge podge of personal opinions (at which point no one should take any of us seriously, as we have made ourselves a joke of standardlessness). The minute we get down to there being an objective reality which we can make authoritative knowledge claims about, we fundamentally therefore arrive at there being correct metaphysical and historiographical positions, and incorrect ones. And if the continued and constant, every day success of science is anything to go by, we know which one is correct.
Thus, the same metric you would use to disprove ancient aliens, is the same metric by which I discount all other non-secular "historiographies" and also various conspiracy theories and the likes.
Now I agree with you that there is no way we as humans can be totally objective, and unbiased. But it is simultaneously true that some of our theories and hypotheses are more objective and true than others. (And if you say ancient aliens theorists, Holocaust deniers, antivaxxers, or any other conspiracy theory is wrong, then you too agree with this statement that there are some positions more objectively true than others.) Which means the tests to be done are in evaluating which theories best correspond to reality by producing consistent and repeatable results. Theology and "Christian historiography" do not end up satisfying this criterion.
Your ending dilemma is also not one. You say:
"The alternative to this is either 1) the imposition of one specific set of theological and philosophical beliefs upon anyone wishing to approach to historical Jesus, as requirement for entry into the discussion, or 2) the construction of a comprehensive argument that demonstrates the superiority of one specific set of theological and philosophical beliefs over all others. The former is undesirable, as it is little more than arbitrary academic gatekeeping; and I don’t think the latter is possible (although I am happy to be proven wrong!)."
Firstly, all of us already construct arguments to demonstrate specific belief systems over others (2). Again, the ancient aliens and Holocaust denial examples are case in points. Serious people don't believe those things, and those who do believe them should not be taken seriously as intellectuals or thinkers. In fact, I don't think you or I would clutch pearls to see an academic espousing those positions removed from their teaching post. (I sincerely hope you wouldn't.) Hence, we also are fine with utilizing variations of (1). Hence, my position: we go with the framework which has produced the most consistent results. And that happens to be secular historiography and it isn't even close by comparison. Not only have secular historiographical methods led to proveable and working reconstructions of the past, but simultaneously the work done has allowed us to even have practical applications like predicting where to find archaeological sites, how to best dig them up, how to contextualize and date papyri, how to better understand ancient languages, etc. The orders of magnitude of gains in secular historiography are too many to count. Meanwhile, doing Christian historiography with a spade in one hand and a bible in the other has a long history of producing extremely dangerous, problematic, false, and often fraudulent results.
Lastly, I will also just add Occam's Razor to the mix. My view comports with known reality and doesn't require anything else. Theological ones require we add a bunch of extra religious and deity stuff none of which has been actually even demonstrated to be a part of reality. Don't multiply objects beyond necessity. Secular historiography produces better and more consistent results, which comport to reality, and does so without the added baggage theological "historiography." Thus, there is no comparison. One is simply better and more efficient.
I don't see much advantage to conversations like these in the end. Accepting your position, we cannot even rationally reason about history or its relation to reality. It is just a jumbled mess of random opinions all with no better footing than the other. This kind of "plurality" is not actually adding anything. There is also simply nothing wrong with methodological authority. In fact, we all already agree it is a good thing. If you are suffering a heart attack and your doctor says, "Well we have to burn sage to cure your miasma and then your heart will be fine," then I think we could all agree that doctor is a quack who should lose their license. Standards and gatekeeping are good actually. And I think it is high time biblical studies got better at both. This postmodernist theologizing is simply a bit bewildering and bewuthering to me. In the end, no one is a postmodernist on the surgeon's table.