I have no idea of what issues were raised in your post which require being addressed. After comparing your response to my post, the only part of your response which seems available to play that role is your last paragraph about ipsy and upsy data. Ok, I will try to make the issues clearer, though I doubt I will make much headway.
First of all, in the set of all problems, there exists an enormous number which have "knowable data": i.e., things which are to be explained by a solution to the problem. That is what problems are all about. To suggest that "knowable data" as I define it is not a possible abstract concept is to hold that the set of all problems is an empty set.
Since 'unknowable data' is defined to be those things which are implied to exist by the solution of the problem, the unknowable data constitutes the things which are not part of the original problem but which must be accepted as existing if the solution which implies them is accepted. They constitute that part of the solution which becomes the "cause" of the events which are to be explained.
The circumstance you bring up, "a problem which contains neither 'knowable data' nor 'unknowable data" is a vacuous concept applying to nothing but an empty entry to the set of all problems.
Finally, the ability to sort things into "knowable" and "unknowable" categories is immaterial to the existence of the categories. A valid solution explicitly requires that both categories obey exactly the same rules: i.e., in the valid solution, there can exist no criteria which can be used to sort the data.
You either did not read or did not understand the essence of the following points made in my post "Third Try".
1) Failure to recognize the difference between "things which are to be explained" and "things which are necessary to the explanation" is fatal to rational problem solving.
2) The division is an abstract fundamental requirement which must be accounted for if the field of possible explanations is to be left unconstrained.
3) The importance of the division is that the two different components are held to different constraints: in laying out the abstract problem of searching for all solutions, the "knowable data" is a fixed component whereas the "unknowable data" must be left open. This fact has nothing to do with actually knowing which is which, it is a characteristic of the logic of problem solving itself.
4.) The only situation when being able to differentiate between the two is of any significance at all is when it comes to solving a specific problem. So long as one is speaking of the logic of problem solving itself, the division must be held open as an abstract concept.
You should be able to comprehend that when a solution to a problem is discovered (and subsequently believed) aspects which, from an abstract perspective were, not known but were required (implied) by the solution acquire the status of known information. If that is going to be the case in all successful solutions, it should be clear to you that it is a requirement of a valid successful solution that, within that solution, there can exist no criteria which can be used to sort the data into the two categories.
However, it should be equally clear to you that, in designing an algorithm which will span all possible solutions of all possible problems, the categories themselves must be held as fundamentally different. The concepts are important to the issue of understanding the range of possibilities available to solve a problem.
Furthermore, consider the situation where one thinks one has discovered a solution to understanding the universe. He then believes all of the things he "knows" are true. Suppose at some time in the future, he discovers his solution is flawed. Does it not follow that some of the things (perhaps all of the things) implied by that solution are false? That is, some of the things he thought he knew were wrong! Now how could it be that some of the things he thought he knew were not true? The only possibility is that those things were not really "knowable", they were in fact, merely consequences of that presumed solution. This is the component of knowledge I give the title "unknowable". To say the category does not exist is to presume that there can be no errors in your solution to the problem.
Finally, let me point out a subtle aspect of this duality of "knowable" and "unknowable" data. The "unknowable" is what is implied by the presumed valid explanation. That is, if the explanation is valid this data is required. Note that if the data is false, then the explanation is invalid. If that is the case, then "unknowable data" may be thought of as that information which was created in order to make the explanation work. That is no more than an alternate perspective on exactly the circumstances common to any scientific explanation.
From that perspective, it should be seen that the scientist has the freedom to create whatever "unknowable data" he desires so long as it will yield the knowable data under the explanation he holds forth. If that is true then the explanation implies both the unknowable and the knowable data are true and it becomes a valid explanation of what is known. The issue here is the trade off between "explanations" and "unknowable data". The fact that such a duality exists is missed by most scientists. The duality will certainly be overlooked if the concept of "unknowable data" is omitted from ones thoughts.
Mike Pearson, I am sorry but I do not understand you or your posts. If they really do make sense, they are far over my head. Say anything you like but please do not expect me to respond. I am personally too mentally limited to see anything but distraction in your posts. You will have to look for someone else to share your humor with.
Alan, I also find your posts to be beyond my comprehension. If there is sense there, it is beyond my ability to see it.
Have fun everybody -- Dick