I'll agree with nwr that falsifiability is not of overriding importance in this case - a minor advantage in falsifiability is not really that big a deal. Both abiogenesis models potentially offer more explanatory power and are more parsimonious. I'd suggest that Lakatos' ideas about research programs are also highly appropriate.
Further I find the difference in falsifiability overstated. First the comparison is between general models and a feature of some panspermia models - albeit ones which are arguably more plausible. Second, the objections raised against the models do suggest that there are potential paths to effectively falsify them - the weight of problems can be sufficient to reject a broad hypothesis even if there is no clear proof against it.
Finally, the call for a more historical approach is not really justified, nor the call to put more effort into panspermia. Both are more dependent on other factors that are not addressed. In the first, the availability of evidence, and in the second concrete and promising research proposals.
quote: And why is it not of significant importance in this case? How do we determine which cases falsifiability should be of impo
Because we are talking about broad models - and because panspermia doesn't seem a lot more falsifiable.
quote: How so?
A working model of abiogenesis seems to be at least potentially more general than a model which only deals with the question of how life arrived on Earth.
quote: Maybe, but only if we operate under the notion that the relative rapid emergence of biological life on Earth is reasonable. A model is more parsimonious because it includes as few unnecessary steps as possible, but a case can be made that the extra time and chemical resources afforded by the panspermia model means that it doesn't add a purely unnecessary step.
That seems a weak argument. Panspermia may offer more time - although that in itself requires assumptions - but it certainly adds in the extra step of getting life from it's putative source to Earth.
quote: And that's the key insight: that the falsifiability of panspermia is based on a model that's been demonstrated to be physically possible
I think you mean that it is the fatal error in your argument. Panspermia is a whole family of models - even directed panspermia is - just as the RNA world and metabolism-first are. Falsifying one of the models doesn't falsify all of them.
So, following your "key insight" lead you to fail to show that panspermia or even directed panspermia were falsifiable.
quote: So which experimental lines in particular do you believe have been carried out that could potentially falsify the RNA world scenario or metabolism first model for the origin of life?
I never claimed to know of any. Rather I refer you to the list of objections in your own post and point out that if they prove too intractable or sufficient additions objections arise the RNA World, for instance, would be effectively falsified (or in Lakatos' terms it would become a degenerate research program and eventually abandoned)
quote: At what point do you conclude that a model's incapacity to generate historical evidence is reflective of the fact that it is not, in fact, historically accurate?
And another misreading. In fact I hold that the ability to make historical enquiries is dependent on the availability of evidence
quote: Well, it could be argued that this is a symptom of the fact that a relatively small amount of effort has been put into investigating the notion of panspermia. Why do you think there has been a lack of promising research proposals for panspermia?
The first objection does not work, If there are ways the effort could usefully be spent there wouldn't be a problem. If there aren't, then there is nothing to spend the effort on. And that is true regardless of whether prior effort has been spent or not,
And I am not making any claims about the existence of research proposals, merely pointing out that the availability of such proposals is a far more important issue than anything you have raised with regard to actually doing research.
quote: Umm, the theory of universal common descent is a fairly broad model, and it's perfectly falsifiable (Karl Popper argued otherwise, but I don't find his argument particularly compelling). Is it your position, then, that the broader a model is, the less falsifiable it needs to be
The more possibilities encompassed by a model the less falsifiable it will be - in general. And yes, I argue that falsifiability is desirable but not a necessity. When we get down to detailed hypotheses it becomes far more necessary.
quote: 1. It would not require assumptions; the thesis that panspermia offers more time is tied to the available evidence we have that indicates that there was a relatively large number of already habitable planets at the time of Earth's origin about 4.5 Ga.
If you're invoking extra-solar planets then I have to ask how you plausibly get life from there to Earth without making assumptions.
quote: 2. You are correct in stating that panserpmia adds in the extra step of getting biological life from a putative source to Earth. But then again, many subsets of abiogenesis models invoke an extraterrestrial source for life's putative organic precursor molecules. Further, if the origin of life outside of Earth is much more realistic instead of an origin of life within Earth, then this additional step the panspermia model adds is not unnecessary -- and therefore does not make the panspermia model particularly less parsimonious than the RNA world or metabolism first scenarios.
Since panspermia doesn't address abiogenesis I'd suggest that steps in abiogenesis are off the table. You can't say that they are "extra" while just taking abiogenesis somewhere else for granted.
quote: is doesn't address my argument that conjuring all sorts of speculative panspermia models isn't exactly a fair way to test the falsifiability of actually plausible panspermia hypotheses.
OK I'll address that point. It is an obvious red herring and completely irrelevant to my objection.
If you are claiming that panspermia is falsifiable you have to show that - not that there are falsifiable scenarios for panspermia.
quote: Okay. So you don't know how the RNA world model could be definitively falsified.
And you concede that my original point was correct, since you can't say anything against it.
quote: So why is the panspermia hypothesis better at generating evidence of a historical nature in contrast to the RNA world and metabolism first models?
Hypotheses don't generate evidence.
quote: That's not necessarily true, though. There can be a priori biases against investigating panspermia based on conformity to scientific orthodoxy.
Your objection fails to address the point. The issue is not the question of whether the work is done, the issue is whether there is potentially useful work to do. And you seemed to want it both ways - suggesting that there was no useful work to do because there was useful work that had yet to be done.
To return to the point, proposals that are never offered can't be rejected due to bias or any other reason. There's no use saying "spend more" with nothing to spend it on.
No, I'm saying that restricting observations to those relating to a single event is a good way to lose generality. By looking only at particular circumstances you limit your ability to understand what would happen if the circumstances were different.
To take an example, if panspermia were true any abiogenesis work relying on conditions on Earth would be of questionable use - the conditions where life really arose may have been different in relevant ways. Work which looked at the possibilities without considering the history of the planet might be more useful in figuring out abiogenesis.
quote: Okay. And do you think that, say, the RNA world model is sufficiently detailed to necessitate the possibility of falsification? If not, why?
By my understanding the RNA World simply postulates that RNA-based replicators preceded DNA-based life. That is certainly general, and I would not expect it to be falsifiable (excepting effective falsification through the weight of problems) given the limitations of the evidence available (other than evidence that lead to it's formation. If, for instance, RNA replicators turned out to be impossible, as seems to have been widely assumed at one time the RNA World would have been clearly falsified.
quote: What kind of assumptions would be made?
Why would you even ask? If you can show that life could get from any or all of the planets in your count to Earth without making additional assumptions please make the case. If you can't then you may as well concede the point. Asking me to concoct scenarios whereby it could happen seems to be an obvious diversion of no worth.
quote: Well, panspermia does mean that biological life from which we descended did not originate on Earth. Abiogenesis -- that is current models like the RNA world scenario -- argues precisely the opposite. So panspermia implies that life necessarily evolved outside of Earth; this, then, increases the likelihood of life ever appearing on Earth, since evolution of biological life beyond Earth could be more chemically realistic.
And if you produce a scenario including abiogenesis that can be evaluated as a who,e we could do that. But until you do, the process of abiogenesis itself can't be compared, and therefore should remain off the table.
quote: You're right: hypotheses don't generate evidence. I didn't word that correctly. So let me re-phrase: why is the evidence for the panspermia hypothesis generally of a historical nature, in contrast to the RNA world and metabolism first models?
That seems obvious. Panspermia leaves out the difficult problem of abiogenesis altogether. If you tried to include it you would find a mu he greater need for possibility-based work. For instance, trying to identify plausible settings where abiogenesis would be easier.
quote: So am I correct in stating that you believe that pursuing panspermia research is a dead-end for pragmatic purposes?
Giving people money just because they favour a particular idea certainly seems to be a poor way of generating useful research. Do you disagree with that ?
Supposedly this post was going o address my points, but it doesn't seem to do so.
First, we have the obvious double standard of demanding that the RNA world and metabolism-first ideas be generally falsifiable while panspermia need only provide falsifiable scenarios. No general falsification for panspermia has been proposed.
Second my point that falsification of such general models effectively occurs when the problems become overwhelming has not really been answered. Following the Duhem-Quine thesis it is usually impossible to falsify general theories, since auxiliary hypotheses can be generated to protect them from falsification (e.g. The epicycles of Ptolmaic cosmology). Given that the falsification I propose is exactly what we'd expect to be required (and both the complexity of the problem and the paucity of evidence add to that) I can't say that there is truly a problem which would lead us to prefer investigations of another model on purely philosophical grounds - the more so since naive falsificationism is hardly considered to be good philosophy in the first place.
quote: Okay. So then, in your view, the RNA world is -- by virtue of its general nature -- not falsifiable except through the accumulation of extensive problems. Yet lithopanspermia is also a rather general model, but as I have argued (contentiously, given objections raised by Dr Adequate), it is falsifiable in the Popperian sense. Thus it would seem to me your primary objection here is that Popperian falsificationism is not an ideal criterion for demarcation of science and non-science. Is this basically correct?
I don't see that lithopanspermia is that general at all. The idea that something akin to existing life travelled on a meteor seems to be quite specific compared to considering the interactions of RNA molecules in all the possible environments found on primordial Earth
And I would say that your statement is sufficiently lacking in nuance to be considered potentially misleading. Thus I am not prepared to agree with it.
quote: That's a pretty terrible way to falsify a hypothesis, since there's no experiment that can potentially demonstrate that RNA replicators are impossible.
Certainly not by exhaustive trial, but we could say that for almost anything.
quote: Because I am genuinely curious if you have discovered assumptions built into lithopanspermia which I am not aware of. However, you appear to prefer a more combative than explorative approach to discussion.
I can't see that asking completely irrelevant questions adds to the discussion. Or that pointing out that they are irrelevant should be considered combative.
quote: So you think there might be particular assumptions in lithopanspermia but you can't establish that. Mmk
No. as I said, if you wish to show that you don't need any extra assumptions it is up to you to offer your explanation. That you choose to divert and evade instead suggests that you don't have any such explanation.
quote: There is evidence that there was a considerable number of life-friendly planets at the time of Earth's origin, which means that abiogenesis would have had more time to occur. This is a rather straightforward argument that panspermia increases the probability of abiogenesis.
How does this address my question that the evidence for panspermia is historical in nature, in contrast to the evidence for the RNA world and metabolism first models? You're response seems to boil down to: "Well, panspermia doesn't address abiogenesis." That appears to be a bit irrelevant to my question. Please elucidate further so I understand what your argument here is.
I haven't really seen much in the way of evidence, but the fact that panspermia has lower theoretical content in relation to historical claims rather suggests that a greater proportion of the evidence should be historical.
quote: No, but that's not what I'm saying, is it? Do you believe that pursuing panspermia research is a dead-end for pragmatic purposes?
But it's been my point and one you seem to have been disputing. I really make no judgement over whether panspermia is a dead end, and making the point that research needs to be proposed before it is funded hardly seems to suggest that I do.
quote: What do you mean by "generally falsifiable" in contrast to "falsifiable scenarios"?
I mean that falsifying lithopanspermia does not in itself falsify panspermia.
quote: By your argument, however, it seems that only the weight of difficulties can bring down the edifice of a hypothesis. But this seems like a pretty poor criterion of demarcation between science and pseudoscience. A "weight of difficulties" can be found in creationism (for which there does not appear to be a compelling falsification scenario), so is creationism therefore science in some way?
No, I mean that - among other reasons - creationism is not science because it HAS been brought down by the weight of difficulties, at least so far as scientific investigation is concerned.
quote: How again is the RNA world model more general than lithopanspermia?
Strictly speaking lithopanspermia doesn't include abiogenesis so much of what you said is irrelevant. And I would say that the whole "travel to earth on a meteorite" - which is the only part you offer as falsifiable - is quite specific.
quote: So then if not by exhaustive trial, how?
By showing some restriction that cannot be overcome.
quote: And the reason panspermia has lower theoretical content in relation to historical claims is what?
Because it doesn't include abiogenesis. If it did *that* part would be even less historical than earthly abiogenesis research.
quote: Sure, and falsifying the RNA world model does not in itself falsify abiogenesis. If you have a falsification scenario for the RNA world model, by all means present it. I will then immediately concede that the RNA world model is falsiViable
By now you certainly ought to realise that I am not claiming that the RNA world is falsifiable. I am claiming that panspermia is not.
quote: Really? Let's take the age of the Earth, for example. No matter how much evidence is presented that the Earth is approximately 4.5 Ga, the creationist can always resort to a divine mechanism (and they have) which accounts for observations of isotope-based dating. You will find that creationists can always account for a particular observation by inserting a divine mechanism, so the weight of the evidence seems to be of no weight at all! The blade that slices creationism away from the domain of science must therefore be the criterion of falsifiability. It is falsifiability, not the weight of evidence, that most starkly divides science from pseudoscience.
If Young Earth Creationism requires loads of ad hoc auxiliary hypotheses to protect it from falsification then it is already not science by my criteria. Why then, do I need to appeal to,any other ?
Edited by PaulK, : Cleaned up an auto "correction"
quote: I don't really understand why this evokes such incredulity from you. The validity of this data as a falsification hinges on the premise that there is no other means of tolerating cosmic radiation aside from certain patterns in the abundance/diversity of proteases, ABC transporters and nucelases. Accepting that premise requires a fair helping of hubris, doesn't it?
I'm sure that exhaustive testing of all the alternatives has been done. After all Genomicus can't think of any other way to falsify the idea that there are alternatives.
quote: You are correct if by "panspermia" you mean the broad idea that life on Earth has a non-terrestrial origin. This idea is as general as abiogenesis (the notion that life arose on Earth through non-directed chemical processes), and so both are not falsifiable. But then again, they are not supposed to be falsifiable as they aren't hypotheses.
Admittedly, I use a different definition of panspermia in the OP -- one that is more appropriately called "lithopanspermia" -- and this is a falsifiable hypothesis, as I have argued in several other posts.
In other words the OP tried to pass off a particular panspermia hypothesis off as panspermia and wrongly compared it to more general ideas which are not expected to be falsifiable, That pretty much accepts my initial criticism.
quote: What matters when it comes to auxiliary hypotheses is that the degree of falsifiability of the original hypothesis is increased. If the auxiliary hypotheses do not do that -- they instead function as an excuse for some difficulty with the hypothesis -- then that hypothesis may be rightly condemned as non-scientific. It all leads back to the criterion of falsifiability.
You know if you want to agree with me it is rather easier to do so explicitly rather than writing two paragraphs which effectively say the same thing without explicit agreement,
I did not say that "many auxiliary hypotheses" were a sufficient condition for the pseudo-science label. I sad that a hypothesis that "requires loads of ad hoc auxiliary hypotheses to protect it from falsification" is pseudoscience.
i thank you for admitting that I was right, but I consider the way of doing it - presenting agreement as disagreement another sign that you are not interested in serious discussion.
quote: Not quite, because comparing lithopanspermia to specific scenarios like the RNA world and metabolism first models is quite reasonable. The RNA world scheme is as highly specific as lithopanspermia, so it really should be falsifiable if we are to accept it as a properly constructed scientific hypothesis.
It is far from obvious that that is true. In fact your whole claim of falsifiability relies on a specific feature of lithopanspermia.
quote: Right. And why does that make it pseudoscience? That, I believe, is where our different positions will become most apparent. I would say that the above scenario -- creationism requiring many auxiliary hypotheses to protect it from reasonable falsification -- makes creationism pseudoscience because of the falsifiability criterion. In other words, these ad hoc auxiliary hypotheses make creationism unfalsifiable, and therefore non-science in the Popperian sense
And yet panspermia is unfalsifiable. String theory is unfalsifiable. And you accept the first as science, and very many scientists accept the second as science. Unfalsifiability in itself is clearly not the clear bright line you are looking for.
Again, you have conceded the point that my criteria are adequate to dismiss YEC as science. Therefore any argument that I need different criteria to do so is obviously fallacious.