Induction and Inertia

[Daniel Barnes]

Roger:

Isn't it understood by all present that the physical universe and the things in it ARE SUCH THAT the Conservation laws hold?

And verily, should it ever be discovered that the Conservations laws do not hold in some circumstances, on day that Roger will be able to declare that it is in the nature and IDENTITY of the Universe for said laws NOT to hold after all!

Behold, the AWESOME philosophic power of the Law of Identity!...;-)

[Daniel Barnes]

Darrell:

I'm not sure I know how to coherently argue against the Humean position...

This is due to the inherent difficulty of arguing against sound logic.

It is an argument that there is an infinite number of swans so that seeing some number of them doesn't tell you anything about swans.

This is simply incorrect. Do you think that just because we can't logically induce universal laws, we can't know anything? Do you think that Newton's theory, while ultimately false, "didn't tell you anything?" This is a classic rhetorical formulation of, ironically, both post-modernists and Randians alike; that just because we often work with false theories, that therefore "we can't know anything." Both seem to think that some kind of "absolute certainty" or "ultimate justification" "true starting point" is necessary for human knowledge to grow, or to even begin. From this common premiss the pomos chicly despair, while the Randians rage against logic itself (eventually trying to invent their own to get round it) But this is a false premiss - it has never been the case.

In fact, we start in error, and try to get closer to the truth.

Therefore, in Popper's words, everything is conjectural.

Thus, if you think this is a problem, you need to check your premisses...;-)

Edited October 2, 2007 by Daniel Barnes

[Dragonfly]

But, this is exactly what we do need to worry about according to Hume and Popper. The problem is that if we can't be sure of anything, then we can't know if we're close either. We could be way off.

No, not being 100% certain doesn't mean that we have no idea how good our model is. When we use it to make predictions and it turns out that these are many times experimentally verified with a high degree of accuracy, we may assume that it is a pretty good model. There is no guarantee that it is a perfect model, that it reflects the "real truth", but we can live with that. Newton worked fine for a long time and is still useful, but we now have some applications where it doesn't work. On the other hand, if you test for example an astrological model the experimental evidence gives only random results which don't correspond to the predictions, so you may conclude that it is a bad model.

[Roger Bissell]

Roger:

Isn't it understood by all present that the physical universe and the things in it ARE SUCH THAT the Conservation laws hold?

And verily, should it ever be discovered that the Conservations laws do not hold in some circumstances, on day that Roger will be able to declare that it is in the nature and IDENTITY of the Universe for said laws NOT to hold after all!

Behold, the AWESOME philosophic power of the Law of Identity!...;-)

Sarcasm duly noted. But, heh, my approach would certainly beat holding that the Conservation laws do not hold in some circumstances for no reason at all.

Having a problem with this omni-contextual trump power of the Law of Identity only arises if you are prone to dropping context when you attempt to philosophize.

When they started blood typing and noting that blood transfusions were deadly when given from people of certain types to another, while other transfusions between certain other types were safe. In the context of the cases they had observed, they were not justified in concluding that all transfusions between type O's, for instance, would be safe, just because the ones they had observed were safe. Lo and behold, they found that some O-O transfusions were deadly. What the...? And that is when they discovered an additional factor, the Rh factor, which made transfusions between Rh negative and Rh positive deadly, even when the ABO type was the same.

Previously, when they over-generalized, they had the equivalent of a BLOOD TRANSFUSION LAW, which said that it is in the nature of human blood that transfusions between certain types are safe and between certain other types are not safe. They had identified the nature of blood that caused certain of those transfusions to be deadly. The Law of Identity at work.

But then they discovered more about the nature of blood that caused certain of the other transfusions to be deadly, too. So, they had to re-formulate their generalization to the SECOND BLOOD TRANSFUSION LAW, which said that it is in the nature of human blood that transfusions between certain types that would be safe if they have the same Rh factor and deadly if they do not. Again, the Law of Identity at work.

You are making it difficult not to psychologize. You seem eager to denigrate and deny the total, universal application of the Law of Identity -- and those who consistently apply it when they do science or philosophy as somehow engaging in circular or ex post facto reasoning. But then, this nothing new, for you and Hume are bent on trashing both Identity and Causality. Funny how you count on them when you communicate your fallacies to us.

REB

[Ellen Stuttle]

Thus I think the answer to why conjectures and refutations are still in place here is to emphasize the IF in the passages I've highlighted:

" [....] IF the thing is understood, predictions can be made. IF it is not, then they cannot."

"IF we understand the nature of things such as the sun, we can make reasonable predictions about them."

We aren't ever entirely sure that our understanding is accurate. (Which doesn't mean we have any reason to lose sleep worrying over the accuracy of our belief in the next day's sunrise.)

But, this is exactly what we do need to worry about according to Hume and Popper. The problem is that if we can't be sure of anything, then we can't know if we're close either. We could be way off.

Sorry; I wasn't clear. I switched contexts between knowledge and belief. What I was indicating is that I don't worry about it. I feel fully comfortable assuming at sunset that "the sun also rises." Apparently, primitive peoples did worry about it; at least especially they worried at the onset of fall if spring would come again, and they performed various rituals believing that their actions would assist to ensure spring's return. I feel comfortable trusting that our understanding of natural "law" is close enough, I can rely on it for all practical purposes.

But I think you're right that universal skepticism does entail that, quoting you, "it could be the case that although momentum has always been conserved in every experiment ever performed that conservation of momentum is an anomaly and that momentum is usually not conserved." Etc. for every other regularity we've thus far found to obtain. My attitude is that should any of these regularities be found not to obtain, I'll cross that bridge when I come to it (assuming I'm here to cross that bridge; i.e., assuming the whole physical world as I've thus far experienced it hasn't vanished in a flash).

I guess what I'm saying is that emotionally I don't find any reason for distress at the implications of universal skepticism. I'm comfortable living my life on the basis "as best as I can ascertain...."

Ellen

PS: You might not have noticed my saying on the "Two Kinds of Induction" thread that I have to bow out of participating in list discussion till after Thanksgiving. I found your reflections too interesting to resist responding. But I have to be sterner with my posting inclinations for the next couple months.

___

[Roger Bissell]

Darrell:

I'm not sure I know how to coherently argue against the Humean position...

This is due to the inherent difficulty of arguing against sound logic.

Hume's logic might be valid in places, but it is not sound. It is riddled with false premises. As Rand said, find the gimmicks, and you can dispense with all of the sophistic philosophies throughout history. Peikoff did a pretty good job of dissecting and dispensing with Hume in his Modern Philosophy lectures. You and Darrell might avail yourselves of them sometime, instead of doing this Eisenhower-Khruschev routine. (Ike professed to be left breathless by Khruschev's arguments against capitalism.)

It is an argument that there is an infinite number of swans so that seeing some number of them doesn't tell you anything about swans.

This is simply incorrect. Do you think that just because we can't logically induce universal laws, we can't know anything? Do you think that Newton's theory, while ultimately false, "didn't tell you anything?" This is a classic rhetorical formulation of, ironically, both post-modernists and Randians alike; that just because we often work with false theories, that therefore "we can't know anything." Both seem to think that some kind of "absolute certainty" or "ultimate justification" "true starting point" is necessary for human knowledge to grow, or to even begin. From this common premiss the pomos chicly despair, while the Randians rage against logic itself (eventually trying to invent their own to get round it) But this is a false premiss - it has never been the case.

In fact, we start in error, and try to get closer to the truth.

It is true that we start in error, or is your notion that we (supposedly) start in error an error, also? What gives your belief about our initial cognitive status -- implying that our knowledge is a gradual process of lessening of error -- anything other than error-status itself? And why should we accept it? I'd appreciate your explanation in terms not subject to error...

Therefore, in Popper's words, everything is conjectural.

Thus, if you think this is a problem, you need to check your premisses...;-)

Is Popper's belief that "everything is conjectural" a conjecture? Or is it a truth, something he knows and you know? If so, what excuses it from self-application and self-contradiction? And if it's just a conjecture, why should any of us accept it? Why, in anything other than conjectural terms, please...

REB

[Daniel Barnes]

Roger:

You are making it difficult not to psychologize. You seem eager to denigrate and deny the total, universal application of the Law of Identity -- and those who consistently apply it when they do science or philosophy as somehow engaging in circular or ex post facto reasoning.

Regardless of speculations as to my psychology, It seems to me that this is exactly the position you've placed yourself in. For, as I say, if it were found that the Conservation laws did not hold, you would indeed claim that this is due to the nature and identity of the universe. Do you deny this? All this shows is that like all attempts to prove everything, applying the LOI in fact proves nothing.

BTW you refer to my "fallacies" yet you have not demonstrated any. All you say is that my arguments do not accord with Objectiivist doctrine. I, on the other hand, have suggested some straighforward logical circularities that seem to occur in your arguments. For example, your inclusion of "a valid concept" as a precondition for "true induction".Yet obtaining a valid concept seems to be the purpose of "true induction." Such a criticism does not require any Popperian doctrine, but is simply a logical one.

How do you respond?

Roger:

Is Popper's belief that "everything is conjectural" a conjecture? Or is it a truth, something he knows and you know?

Ah, the naiive skeptical refutation lives! I am always suprised - though I shouldn't be by now, I suppose - when this is wielded as if it was somehow a mighty reply, when it is really on about the same level as the Fool's Mate in chess.

For the nth time: being skeptical about skepticism is logically unproblematic. Skepticism is indeed conjectural, and may turn out to be false. Thus there is no contradiction in holding it.

And if it's just a conjecture, why should any of us accept it?

No one is making you accept anything. You don't have to accept the logical arguments for skepticism, nor the rules of logic itself if you don't want to.

For the time being however, it's the best tested theory....;-)

Edited October 2, 2007 by Daniel Barnes

[tjohnson]

Is Popper's belief that "everything is conjectural" a conjecture?

Interesting, this amounts to a question of "knowledge of things" vs. "knowledge of knowledge". If our knowledge of things is conjectural it does not follow that our knowledge of knowledge is also, these are two different kettles of fish.

[Roger Bissell]

Is Popper's belief that "everything is conjectural" a conjecture?

Interesting, this amounts to a question of "knowledge of things" vs. "knowledge of knowledge". If our knowledge of things is conjectural it does not follow that our knowledge of knowledge is also, these are two different kettles of fish.

I knew there was something fishy about your whole position! :-)

While it may not logically follow from knowledge of things being conjectural that knowledge of knowledge is also conjectural, it may in fact be the case that knowledge of knowledge is conjectural. One would expect Popper (and you) to either be consistent in holding that all knowledge is conjectural -- or to come up with a convincing explanation as to why the former is and the latter isn't! Instead, you duck the question (and please pardon the mixed zoological metaphor).

You reveal too much.

REB

[Daniel Barnes]

Is Popper's belief that "everything is conjectural" a conjecture?

Interesting, this amounts to a question of "knowledge of things" vs. "knowledge of knowledge". If our knowledge of things is conjectural it does not follow that our knowledge of knowledge is also, these are two different kettles of fish.

Why do you think that? We can critically study how we obtain knowledge. We can have false theories of epistemology, just as we can have false theories of physics. Epistemology has no sacred status.

[Darrell Hougen]

]It is an argument that there is an infinite number of swans so that seeing some number of them doesn't tell you anything about swans.

This is simply incorrect. Do you think that just because we can't logically induce universal laws, we can't know anything? Do you think that Newton's theory, while ultimately false, "didn't tell you anything?" This is a classic rhetorical formulation of, ironically, both post-modernists and Randians alike; that just because we often work with false theories, that therefore "we can't know anything." Both seem to think that some kind of "absolute certainty" or "ultimate justification" "true starting point" is necessary for human knowledge to grow, or to even begin. From this common premiss the pomos chicly despair, while the Randians rage against logic itself (eventually trying to invent their own to get round it) But this is a false premiss - it has never been the case.

In, "The Problem of Induction," (http://dieoff.org/page126.htm) Popper states:

[Hume] believed that induction by repetition was logically untenable - that rationally, or logically, no amount of observed instances can have the slightest bearing upon unobserved instances. This is Hume's negative solution of the problem of induction, a solution which I fully endorse.

That sounds pretty much like what I said. Moreover, that view is extreme. My argument is that even though we may not have the exact formulation of the correct law, we know that we are close. Any exceptions must be small or must occur infrequently. Otherwise, we would have seen evidence of them earlier. But, that amounts to a statement that we actually know something and that our knowledge is a result of our observations. Moreover, our knowledge is not conjectural.

In the same article, Popper states:

Take as an example classical Newtonian mechanics. There never was a more successful theory. If repeated observational success could establish a theory, it would have established Newton's theory. Yet Newton's theory was superseded in the field of astronomy by Einstein's theory, and in the atomic field by quantum theory. And almost all physicists think now that Newtonian classical mechanics is no more than a marvellous conjecture, a strangely successful hypothesis, and a staggeringly good approximation to the truth.

How does Popper know that Newtonian mechanics is, "a staggeringly good approximation to the truth?" It would seem that he cannot, according to his own philosophy. If Newtonian mechanics is, "a mere conjecture," there is no way of knowing how close it is to being correct. You can't have it both ways and neither can Popper.

Darrell

[Darrell Hougen]

But, this is exactly what we do need to worry about according to Hume and Popper. The problem is that if we can't be sure of anything, then we can't know if we're close either. We could be way off.

No, not being 100% certain doesn't mean that we have no idea how good our model is. When we use it to make predictions and it turns out that these are many times experimentally verified with a high degree of accuracy, we may assume that it is a pretty good model.

On what basis may we make that assumption?

I basically agree with you, but I think your opinion contradicts much of what Popper is saying. There must be unstated principles that are being used to arrive at such conclusions.

Darrell

[Darrell Hougen]

Sorry; I wasn't clear. I switched contexts between knowledge and belief. What I was indicating is that I don't worry about it. I feel fully comfortable assuming at sunset that "the sun also rises." ...

But I think you're right that universal skepticism does entail that, quoting you, "it could be the case that although momentum has always been conserved in every experiment ever performed that conservation of momentum is an anomaly and that momentum is usually not conserved." Etc. for every other regularity we've thus far found to obtain. My attitude is that should any of these regularities be found not to obtain, I'll cross that bridge when I come to it (assuming I'm here to cross that bridge; i.e., assuming the whole physical world as I've thus far experienced it hasn't vanished in a flash).

...

PS: You might not have noticed my saying on the "Two Kinds of Induction" thread that I have to bow out of participating in list discussion till after Thanksgiving. I found your reflections too interesting to resist responding. But I have to be sterner with my posting inclinations for the next couple months.

I think your view is very Humean and I don't agree. Thank you, however, for your contributions to this discussion and I look forward to talking with you in the future.

Darrell

[Roger Bissell]

I wrote:

You are making it difficult not to psychologize. You seem eager to denigrate and deny the total, universal application of the Law of Identity -- and those who consistently apply it when they do science or philosophy as somehow engaging in circular or ex post facto reasoning.

Daniel replied:

Regardless of speculations as to my psychology, It seems to me that this is exactly the position you've placed yourself in. For, as I say, if it were found that the Conservation laws did not hold, you would indeed claim that this is due to the nature and identity of the universe. Do you deny this? All this shows is that like all attempts to prove everything, applying the LOI in fact proves nothing.

"Like all attempts to prove everything"?? Are you saying that proof of any kind is futile and fruitless? What is your support for this argument? Is it an inductive argument -- or deductive (and from what premises) -- or is it an axiom of your Humean-skeptic faith?

The purpose of the LOI is not to "prove" anything. It is the basis of proof. Without it (i.e., without at least implicitly acknowledging it), there is no proof and no knowledge. Consciousness and knowledge in particular is a grasping of the identity of something, and proof (whether deductive or inductive) is establishing what the identity of certain things must be if the identity of certain other things is the case. When we drag out the Law of Identity, or the Law of Contradiction, it is to check our work, to make sure that an error has not been made. And when we try to deny these laws, as Aristotle pointed out with his famous principle of Reaffirmation Through Denial, we find that we cannot logically do so. We "reaffirm" them in the act of denial.

Every context of knowledge is knowledge of things having a certain nature, and we know more or less of that nature at any given time, and when our context expands, we have to revise our formulation of our knowledge (as in the blood typing example I used). We cannot legitimately claim to know more than our context allows, but we should be confident in claiming what we do know.

And there is no justification for calling our limited knowledge "error," just because some particular conclusions are incorrectly framed as over-generalizations. For instance, if I said in pre-Rh-knowledge days, "All the B-A transfusions we have seen so far are deadly, while all the B-B transfusions we have seen so far are safe," I would have been within my epistemological rights and in good position to amend that valid statement with another: "Some B-B transfusions are not safe" (because of differing Rh factor). But if I had started out with an overly confident generalization: "All B-B transfusions are safe," I would have been quite crestfallen when I discovered the deadly Bneg-Bpos transfusions. Perhaps I would have even succumbed to your siren song of how our knowledge is all "error seeking toward truth." Or, I could have taken the more reasonable position and realized that I over-generalized, and that the error was not in assuming I could discover valid knowledge of reality, but in simply jumping to conclusions in this particular case.

Daniel wrote:

BTW you refer to my "fallacies" yet you have not demonstrated any. All you say is that my arguments do not accord with Objectiivist doctrine. I, on the other hand, have suggested some straighforward logical circularities that seem to occur in your arguments. For example, your inclusion of "a valid concept" as a precondition for "true induction".Yet obtaining a valid concept seems to be the purpose of "true induction." Such a criticism does not require any Popperian doctrine, but is simply a logical one.

How do you respond?

By first biting my tongue....OK, there is no logical circularity in the Objectivist or Aristotelian models of concept-formation and induction, and the purpose of induction is not to obtain concepts. The purpose of concepts and generalization (inductive generalization) is to gain information we can use to survive and enjoy our lives. (Reason, the capacity for forming concepts, generalizations, and reasoning from them, is our tool of survivel.)

There is a parallel between moving from concretes to concepts and narrower concepts to broader concepts, on the one hand, and moving from concretes to generalizations and narrower generalizations to broader generalizations, on the other. But only the latter is what we are referring to when we speak of "induction" in the context of logic. Valid concepts are a "green light" to (a precondition of) valid induction/generalization, as Peikoff puts it in his induction lectures.

It is true that later concepts come along, after we have formed some generalizations, and that we couldn't form some of those concepts unless we had integrated our concepts into generalizations and then pursued more knowledge. But even our later concepts are dependent fundamentally on our earliest concepts, and only secondarily or derivatively on the generalizations that followed them.

A note about Randspeak: she did refer in ITOE (p. 28) to induction and deduction as "fundamental methods of cognition," but she was not referring there specifically to forming generalizations/principles/laws and to constructing syllogisms, but instead more generally to conceptually integrating one's observations and applying them to new situations. Only in this sense is it true that we use "induction" (conceptual integration) to obtain concepts -- as we also use "induction" when we integrate our concepts into generalizations/principles/laws. But I regard this as misleading and I would avoid referring to concept-formation as "essentially" a process of "induction." They are similar in going from narrower to broader. Saying any more than that is asking to be misunderstood. In his two sets of lectures on induction, Peikoff is careful to identify the structure of induction as being analogous or similar to that of concept-formation, not as the genus of concept-formation.

REB

[tjohnson]

[Why do you think that? We can critically study how we obtain knowledge. We can have false theories of epistemology, just as we can have false theories of physics. Epistemology has no sacred status.

Can we do experiments in epistemology? Are epistemological theories falsifiable a la Popper? I don't see how.

[Daniel Barnes]

Darrell:

My argument is that even though we may not have the exact formulation of the correct law, we know that we are close.

Any exceptions must be small or must occur infrequently.

Otherwise, we would have seen evidence of them earlier.

The obvious reply to all of the above is: why? These are merely a series of bald assertions, with nothing whatsoever necessary about them.Where's the argument?

But, that amounts to a statement that we actually know something and that our knowledge is a result of our observations. Moreover, our knowledge is not conjectural.

This merely is a confusion over shades of meaning of "knowledge". Plato thought there were two types of knowledge: "episteme" and "doxa", or knowledge in the ultimate, transcendent sense, and mere mortal opinion.

Popper says the only thing humans have to work with is opinion., although we can aim at getting more and more accurate opinions. He says we have no way of attaining "episteme", except perhaps by incredible luck, where our opinions happen to coincide with the absolutely true state of affairs. And even then, we'd never be quite sure we'd hit on it. Hence:

How does Popper know that Newtonian mechanics is, "a staggeringly good approximation to the truth?"

So you see it is, in his opinion (and that of many others), staggeringly close to the truth. He may even experience the passionate sense of conviction that it is close to the truth. But of course, neither his sense of conviction nor his opinion nor that of others justifies it.

So he does not have it both ways, but is in fact perfectly consistent.

Edited October 3, 2007 by Daniel Barnes

[Daniel Barnes]

GS:

Can we do experiments in epistemology? Are epistemological theories falsifiable a la Popper?I don't see how.

You can indeed experiment in epistemology. For example, I think that Rand's theory of concept formation is could be empirically tested. I have proposed a couple of such experiments myself. (I think it would almost certainly fail empirical testing, incidentally)

Of course, not all epistemologies (nor even all elements of particular epistemologies) are necessarily falsifiable. I would think a good deal aren't.

[Michael Stuart Kelly]

Daniel,

It boils down to accepting the following law of nature or not.

Ontologically, the small stuff of the universe is arranged in entities that act, background and hierarchies of organization. (I believe Popper called this top down views "laws of the universe" or "laws of nature" or something like that).

If you accept that, you can identify categories in the same manner you can identify a single concrete. If you do not accept that, you merely have isolated observations of unrelated things and a theory hinged on a root of "we ultimately cannot be sure of anything, even this statement about not being sure, and even about what this statement means."

It's a choice. I say science is not only based on observation, but categories as well.

Michael

[tjohnson]

You can indeed experiment in epistemology. For example, I think that Rand's theory of concept formation is could be empirically tested. I have proposed a couple of such experiments myself. (I think it would almost certainly fail empirical testing, incidentally)

Of course, not all epistemologies (nor even all elements of particular epistemologies) are necessarily falsifiable. I would think a good deal aren't.

I would be interested in your idea of an epistemological experiment. Korzybski's "defining your terms" experiment shows that we eventually define in circles - not sure if that qualifies as epistemological or not. But in general I don't think you can have a science, in the sense of experiments, of epistemology. It seems to be mostly just a bunch of arbitrary verbalisms. Korzybski basically said that "to know is to know structure", ie. there is nothing else for us to know. We perceive structure and we speak structure and the 'similarity of structure' is how we judge the value of any body of knowledge. Thus Newton's physics is less similar in structure than Einstein's - there is no need to speak about 'true' and 'false'.

[BaalChatzaf]

I would be interested in your idea of an epistemological experiment. Korzybski's "defining your terms" experiment shows that we eventually define in circles - not sure if that qualifies as epistemological or not. But in general I don't think you can have a science, in the sense of experiments, of epistemology. It seems to be mostly just a bunch of arbitrary verbalisms. Korzybski basically said that "to know is to know structure", ie. there is nothing else for us to know. We perceive structure and we speak structure and the 'similarity of structure' is how we judge the value of any body of knowledge. Thus Newton's physics is less similar in structure than Einstein's - there is no need to speak about 'true' and 'false'.

That sounds like a version of the Correspondence Theory of Truth. Which goes back to Aristotle (at least that far back).

Ba'al Chatzaf

[tjohnson]

It's a choice. I say science is not only based on observation, but categories as well.

Michael

I take this to mean that you believe categories exist independent of observer? Can this ever be decided either way? We look around us we see different things with common characteristics and so we categorize. This all happens together as part of a process which Korzybski calls 'abstracting'. So you have the objects, the observers, and the categories as parts of the phenomenon of human consciousness. You don't ever have one without the other 2.

Look at the equation in physics f=ma. All 3 terms are inter-related, you can't have 1 without the other 2. So you could say that Consciousness is a function of Abstracting from Reality, or something like that.

[Michael Stuart Kelly]

GS,

I believe that there are species of life forms whether there is an observer or not. I believe there are stars whether there is an observer or not. I believe in some kind of top-down organization of existence and that we are able to perceive it and form concepts of it because we are part of it. Our mind's organization reflects reality's organization because the same laws of nature govern both.

Michael

[tjohnson]

GS,

I believe that there are species of life forms whether there is an observer or not. I believe there are stars whether there is an observer or not. I believe in some kind of top-down organization of existence and that we are able to perceive it and form concepts of it because we are part of it. Our mind's organization reflects reality's organization because the same laws of nature govern both.

Michael

Yes, that's pretty well what I thought your position was. I don't think there is any way to resolve this issue. I can keep saying there is SOMETHING there whether there is an observer or not, but if there is no observer there can be no discussing it either, right? The moment you say 'star', an observer is implied. Isn't that an instance of 'stolen concept'?

[Daniel Barnes]

GS:

I would be interested in your idea of an epistemological experiment.

Rand's epistemological theory makes certain - admittedly vague - predictions. We could design tests to see if they come true. Hence we can experimentally test her epistemology in reality.

[Dragonfly]

No, not being 100% certain doesn't mean that we have no idea how good our model is. When we use it to make predictions and it turns out that these are many times experimentally verified with a high degree of accuracy, we may assume that it is a pretty good model.

On what basis may we make that assumption?

Because that is in fact the way we define what a good model is. How do we arrive at the notion of an external reality that is independent of our consciousness? It is the result of our observation that there are consistent regularities in the way our environment reacts to our actions, so that we can often predict succesfully what will happen when we perform a certain action. This can be in the form of simple intuitive models that we more or less unconsciously create on the basis of our experience ("folk physics"), like the notion that objects tend to fall if they are released in mid-air, or the more elaborate and sophisticated models that are developed in science. We summarize for example the consistent behavior of falling objects as the notion of "gravity"; so far only a name for the universal "falling behavior" that we see around us. More sophisticated models can give us more information, enabling us not only to predict that something will fall, but for example also how fast it will fall, and also explaining why some objects (like a helium balloon) don't fall, but rise.

The notion of an independent reality is an extrapolation of our consistent experiences and successful models. There seems to be some invariant core in our experiences that we may approach more and more closely, but that remains in fact an abstraction. So if we have a model that can make consistently succesful and accurate predictions, this is by definition a good representation of reality, there is no other way to define "reality as far as we know it" (RAFAWKI). Now we know from experience in the course of centuries that there is no guarantee that later experience or experiments may not invalidate or at least limit the validity of such a model, so there is no reason to assert that our latest model is the definitive, correct model. For convenience we call in daily life RAFAWKI just "reality", but we should keep in mind that RAFAWKI is at best only an approximative representation of metaphysical reality. That reality is an abstraction.

I basically agree with you, but I think your opinion contradicts much of what Popper is saying. There must be unstated principles that are being used to arrive at such conclusions.

I don't know what Popper is saying, I'll leave that to our resident Popper specialist.