How do we know X existed?

[neilgodfrey]

Actually, I'll start a separate thread on what I'm asking. It is part of the implications of the primacy of Marcion's Gospel, but the concepts deserve their own consideration. Neil is most welcome to join in! It least for his first three responses!

Or why not revive this thread that got kind of sidetracked by other issues?

Part of the answer: No, Bayes is not used by historians to determine if X existed. All Bayes can do is assess the probability of a hypothesis. Historians don't build their hypotheses on "persons who probably existed" and "events that probably happened".

Other part of the answer. See the OP to this thread.

[neilgodfrey]

Let's be clear:

In a theoretical sense we can know nothing about the past. In a theoretical sense we can only speak of what probably happened and who probably existed.

But in the real world we don't believe that. A jury must convict for a past crime "without reasonable doubt". There is either conviction or acquittal. No in-betweens in the real world.

If there is not enough evidence to remove all doubt then it is not safe to convict.

Evidence does not need to be overwhelming in abundance, either. A single fingerprint or DNA swab may be all that it takes to remove all doubt.

Hence it is reasonable to conclude that Pythagoras was a historical figure because we have a known historian, writing centuries after the supposed time of Pythagoras, cited a contemporary of Pythagoras speaking about that same P in his real world. It is reasonable, from what we know of that historian, that he was indeed using a valid source by a known person from the time of P.

That is reasonable evidence for the historicity of P.

If we had anything comparable for Jesus then I suggest there would never have arisen a debate about his historicity.

[mlinssen]

Let's be clear:

In a theoretical sense we can know nothing about the past. In a theoretical sense we can only speak of what probably happened and who probably existed.

But in the real world we don't believe that. A jury must convict for a past crime "without reasonable doubt". There is either conviction or acquittal. No in-betweens in the real world.

If there is not enough evidence to remove all doubt then it is not safe to convict.

Evidence does not need to be overwhelming in abundance, either. A single fingerprint or DNA swab may be all that it takes to remove all doubt.

Hence it is reasonable to conclude that Pythagoras was a historical figure because we have a known historian, writing centuries after the supposed time of Pythagoras, cited a contemporary of Pythagoras speaking about that same P in his real world. It is reasonable, from what we know of that historian, that he was indeed using a valid source by a known person from the time of P.

That is reasonable evidence for the historicity of P.

If we had anything comparable for Jesus then I suggest there would never have arisen a debate about his historicity.

And that is exactly it - and we can see how even the falsifying fathers adhered to that by e.g. Origen allegedly citing an alleged Celsus, and how that is used by historicists (not historians) to allege the alleged historical existence of said alleged Celsus

The issue there, however, is the lack of objectivity and impartiality: just as a fingerprint or DNA is entirely impartial evidence there is always the possibility that its existence in a crime scene is not because it got put there, and the planting of drugs by police is a fine example of that

So what is needed in attestations is impartiality, a certain lack of motive to the very act behind attesting

[GakuseiDon]

Compare this:

Part of the answer: No, Bayes is not used by historians to determine if X existed. All Bayes can do is assess the probability of a hypothesis. Historians don't build their hypotheses on "persons who probably existed" and "events that probably happened".

... with this:

Hence it is reasonable to conclude that Pythagoras was a historical figure because we have a known historian, writing centuries after the supposed time of Pythagoras, cited a contemporary of Pythagoras speaking about that same P in his real world. It is reasonable, from what we know of that historian, that he was indeed using a valid source by a known person from the time of P.

That is reasonable evidence for the historicity of P.

That IS Bayesian analysis, isn't it? The one thing that struck me when reading Dr Carrier's description of its use is that it is how we think about propositions anyway. Bayes is simply a formalisation of what you have done with Pythagoras.

So I'd say your example of Pythagoras is the proof that Bayes Theorem could be used to examine historical questions. The issue is whether there is enough solid data to evaluate the question of a historical Jesus in the first place.

(Note: People read Carrier's OHJ and assume that that what he is doing is calculating the chances that there was a historical Jesus, but he isn't. He is comparing the strength of the minimalist mythicist theory against the minimalist historicist theory and deriving a figure from that. It doesn't tell us directly what the possibility of a historical Jesus is.)

[neilgodfrey]

Let's be clear:

In a theoretical sense we can know nothing about the past. In a theoretical sense we can only speak of what probably happened and who probably existed.

But in the real world we don't believe that. A jury must convict for a past crime "without reasonable doubt". There is either conviction or acquittal. No in-betweens in the real world.

If there is not enough evidence to remove all doubt then it is not safe to convict.

Evidence does not need to be overwhelming in abundance, either. A single fingerprint or DNA swab may be all that it takes to remove all doubt.

Hence it is reasonable to conclude that Pythagoras was a historical figure because we have a known historian, writing centuries after the supposed time of Pythagoras, cited a contemporary of Pythagoras speaking about that same P in his real world. It is reasonable, from what we know of that historian, that he was indeed using a valid source by a known person from the time of P.

That is reasonable evidence for the historicity of P.

If we had anything comparable for Jesus then I suggest there would never have arisen a debate about his historicity.

And that is exactly it - and we can see how even the falsifying fathers adhered to that by e.g. Origen allegedly citing an alleged Celsus, and how that is used by historicists (not historians) to allege the alleged historical existence of said alleged Celsus

The issue there, however, is the lack of objectivity and impartiality: just as a fingerprint or DNA is entirely impartial evidence there is always the possibility that its existence in a crime scene is not because it got put there, and the planting of drugs by police is a fine example of that

So what is needed in attestations is impartiality, a certain lack of motive to the very act behind attesting

Even if Origen were as honest as the day is long his reference to Celsus would not count as evidence for the historicity of Jesus. Celsus was never thought to be a contemporary or eyewitness of Jesus. All Celsus could do is tell us what a person in his own time thought -- via Origen.

[neilgodfrey]

Compare this:

Part of the answer: No, Bayes is not used by historians to determine if X existed. All Bayes can do is assess the probability of a hypothesis. Historians don't build their hypotheses on "persons who probably existed" and "events that probably happened".

... with this:

Hence it is reasonable to conclude that Pythagoras was a historical figure because we have a known historian, writing centuries after the supposed time of Pythagoras, cited a contemporary of Pythagoras speaking about that same P in his real world. It is reasonable, from what we know of that historian, that he was indeed using a valid source by a known person from the time of P.

That is reasonable evidence for the historicity of P.

That IS Bayesian analysis, isn't it? The one thing that struck me when reading Dr Carrier's description of its use is that it is how we think about propositions anyway. Bayes is simply a formalisation of what you have done with Pythagoras.

No. (Unless we acknowledge that all sound reasoning is Bayesian at some level, in which case the term loses any useful meaning.)

No, the evidence cited tells us that we have a trusted contemporary eyewitness of Pythagoras. That tells us he existed. There is no 80% probability he existed on that evidence. It's either/or. (Unless, as I pointed out about being theoretical, in which case we would say it is 99% certain he existed as it is 99% certain the moon is made of rock and not cheese and 99% certain ScoMo is PM of Australia. That's nice for a theoretical discussion but historians' data is real; it is not theoretical like their hypotheses may be.)

So I'd say your example of Pythagoras is the proof that Bayes Theorem could be used to examine historical questions. The issue is whether there is enough solid data to evaluate the question of a historical Jesus in the first place.

You can say anything you like but we are not doing a Carrier-like analysis of the evidence, are we.

(Note: People read Carrier's OHJ and assume that that what he is doing is calculating the chances that there was a historical Jesus, but he isn't. He is comparing the strength of the minimalist mythicist theory against the minimalist historicist theory and deriving a figure from that. It doesn't tell us directly what the possibility of a historical Jesus is.)

A difference without a distinction. He is evaluating hypotheses.

[GakuseiDon]

Bayes is simply a formalisation of what you have done with Pythagoras.

No. (Unless we acknowledge that all sound reasoning is Bayesian at some level, in which case the term loses any useful meaning.)

All sound reasoning IS Bayesian. If it can't be expressed in Bayesian terms, it probably isn't sound.

From Dr Richard Carrier's "Proving History", page 68:

As one analyst put it, BT actually explains “what are regarded as sound methodological procedures” and reveals “the infirmities of what are acknowledged as unsound procedures” in almost any empirical field. 1 In other words, Bayes's Theorem underlies all other methodologies and thus explains why certain methods are regarded as sound, and others not—even when advocates or detractors of various methods are unaware of BT's capability in this regard. This entails a testable prediction, that all valid empirical methods reduce to BT: any method you propose will either be logically invalid or it will be described by BT.

No, the evidence cited tells us that we have a trusted contemporary eyewitness of Pythagoras. That tells us he existed. There is no 80% probability he existed on that evidence. It's either/or. (Unless, as I pointed out about being theoretical, in which case we would say it is 99% certain he existed as it is 99% certain the moon is made of rock and not cheese and 99% certain ScoMo is PM of Australia. That's nice for a theoretical discussion but historians' data is real; it is not theoretical like their hypotheses may be.)

So, why not use 100% in your Bayesian calculation on that point? Why do you have to use 99%? If it's one element amongst many others that goes against it, it will come out in the wash.

[mlinssen]

Even if Origen were as honest as the day is long his reference to Celsus would not count as evidence for the historicity of Jesus. Celsus was never thought to be a contemporary or eyewitness of Jesus. All Celsus could do is tell us what a person in his own time thought -- via Origen.

I think that Origen's entire goal was to denigrate and obfuscate certain sayings by attributing them to a heretic. I doubt that Celsus or any of his alleged work existed

Origen attests to Thomas - if your read between the lines. I'd have to re read the parts to exemplify and motivate, might do that later on today

[Paul the Uncertain]

You can say anything you like but we are not doing a Carrier-like analysis of the evidence, are we.

Carrier-like is not a synonym for Bayesian.

For one thing relavant to this old thread, and which came up again recently in another thread, he sets aside the entire issue of conditional (in)dependence when combining pieces of evidence. For another, he's number-bound in a domain where there are few if any useful numbers. He uses an interval-etimate work-around, which is OK, but he clearly lives in an intellectual void where DeFinetti and Polya (two innovators in adapting probabilistic methods to non-numerical relations) don't influence him at all.

(He's doing Newtonian physics for a problem domain which requires something more modern, if you will.)

So, it may not be 80%-20% that Jesus existed, but why is it not (what is the principled objection to) statements about the human past like "It is more likely ( = the speaker has more confidence that ) Queen Elizabeth I of England existed than that Socrates existed, and more likely that Socrates existed than that Jesus did?"

(And btw, such statements are isomorphic to an algebraic system of linear inequalities, and so can define a set of numerical probabilites, and so given enough of them, maybe Jesus is 80%-20% in the sense of being a possible solution of that system of inequalities. The existence of that chain of isomorphisms is not optional - you can use it or not, but it exists despite anyone's choice about whether to use or not to use "Bayes.")

[mlinssen]

Even if Origen were as honest as the day is long his reference to Celsus would not count as evidence for the historicity of Jesus. Celsus was never thought to be a contemporary or eyewitness of Jesus. All Celsus could do is tell us what a person in his own time thought -- via Origen.

I think that Origen's entire goal was to denigrate and obfuscate certain sayings by attributing them to a heretic. I doubt that Celsus or any of his alleged work existed

Origen attests to Thomas - if your read between the lines. I'd have to re read the parts to exemplify and motivate, might do that later on today

Forget it! I was thoroughly confused and under the impression that "Celsus" was contained in a handful of pages alone - the 500+ actual pages prevent me from following up on my claim.
So,