Harv, you have really have disappointed me here. I had expected you to think things out a bit more carefully. You are supposed to be my expert on philosophy. That should imply a modicum of serious thought! You put forth the idea that only "physical things" need explanation (and, indeed, you do this without bothering to explain to me what you mean by "physical". Out of curiosity, would you please let me know how you feel "physical" is to be defined without an explanation of what you are talking about? Think about it a little.
I also feel you are confusing yourself when you hold that one cannot refer to something which is undefined. I have in my mind a hieroglyphic text which I have seen used in several different places; however, what it means is presently beyond my knowledge. I would call it undefined and yet I can refer to what it means (in fact, I just did) and I think further study of its use might indeed lead me to understand what it means. In your world, your logical position seems to be that it must be referring to a "physical thing" or it would require no explanation. That seems to be an extremely limited view of the concept normally referred to by the term "explanation".
You say, "I don't know what you want 'explanation' to mean if you cannot refer to physical things". Certainly you cannot explain "physical things" until after you have explained what a "physical thing" is and thus your concept of an explanation is wholly inadequate. You ask for a definition of explanation in the absence of a definition of "physical". I thought I made my concept of an explanation quite clear: "I define 'An explanation' to be a method of obtaining expectations from given known information". (Expectations are answers to some questions and neither the answers nor the questions need to be defined for one to comprehend the relationship herein implied.) If you can think of an "explanation" which does not fall under that definition, let me know.
It seems to me that some of the difficulties you have understanding my presentation are discussed in the "Stanford Encyclopedia of Philosophy" under "The Regress Problem". To quote the discussion under Aristotle's logic:
In Posterior Analytics I.2, Aristotle considers two challenges to the possibility of science. One party (dubbed the "agnostics" by Jonathan Barnes) began with the following two premises:
1. Whatever is scientifically known must be demonstrated.
2. The premises of a demonstration must be scientifically known.
They then argued that demonstration is impossible with the following dilemma:
1. If the premises of a demonstration are scientifically known, then they must be demonstrated.
2. The premises from which each premise are demonstrated must be scientifically known.
3. Either this process continues forever, creating an infinite regress of premises, or it comes to a stop at some point.
4. If it continues forever, then there are no first premises from which the subsequent ones are demonstrated, and so nothing is demonstrated.
5. On the other hand, if it comes to a stop at some point, then the premises at which it comes to a stop are undemonstrated and therefore not scientifically known; consequently, neither are any of the others deduced from them.
6. Therefore, nothing can be demonstrated.
A second group accepted the agnostics' view that scientific knowledge comes only from demonstration but rejected their conclusion by rejecting the dilemma. Instead, they maintained:
Demonstration "in a circle" is possible, so that it is possible for all premises also to be conclusions and therefore demonstrated.
Aristotle does not give us much information about how circular demonstration was supposed to work, but the most plausible interpretation would be supposing that at least for some set of fundamental principles, each principle could be deduced from the others.
Aristotle rejects circular demonstration as an incoherent notion on the grounds that the premises of any demonstration must be prior (in an appropriate sense) to the conclusion, whereas a circular demonstration would make the same premises both prior and posterior to one another (and indeed every premise prior and posterior to itself). He agrees with the agnostics' analysis of the regress problem: the only plausible options are that it continues indefinitely or that it "comes to a stop" at some point. However, he thinks both the agnostics and the circular demonstrators are wrong in maintaining that scientific knowledge is only possible by demonstration from premises scientifically known: instead, he claims, there is another form of knowledge possible for the first premises, and this provides the starting points for demonstrations.
In my opinion, Aristotle's position is ludicrous as it merely ignores the problem: i.e., "another form of knowledge" is clearly not a defendable source and simply amounts to nothing more than an assumption that one "knows" the correct answer a-priori; a rather overwhelming assumption. From our discussion I have come to the conclusion that you believe Aristotle's position to be the only valid conclusion.
My position is akin to the idea of circular demonstration; however, instead of requiring that "for some set of fundamental principles, each principle could be deduced from the others", I point out that there exists no explanation of anything which cannot be mapped into my model. That is to say that what one chooses as "fundamental principles", is immaterial to the final solution. No matter what that solution might be, it can be mapped into the model I present.
The essence of my position is that any logical construct no matter what axioms it is based on can be modeled by my model and, as I can clearly demonstrate a mapping of my model into modern physics, any explanation can be mapped into our current accepted world view of reality. This opens the door to an infinite number of possible solutions. The only differences in that collection of solutions is the complexity of the predicted consequences: in other words, the predictive value of the perspective.
Once one accepts the validity of my work, some serious philosophical issues come up which are quite at odds with currently accepted ideas of reality. I had hoped to discuss some of this with someone.
Sorry it took me so long to get back!
Have fun -- Dick