This is an interesting discussion, but I think we may be spinning our wheels. Euphoriet's questions are excellent and deserve to be examined even now after many centuries of study. Hypnagogue's suggestion that we should start with an understanding of that historical work is a good one, but it would be a mistake to assume that any of that work has produced correct or even useful answers to Euphoriet's questions. One thing that becomes clear as you study the references Hypnagogue provided is that much of the past inquiry has devolved to questions of etymology and tradition and, in my humble opinion, borders dangerously close to sophistry. I don't think it is very useful to our inquiry.
At our particular point in history, we have the huge unprecedented advantage of the advances of modern science and mathematics. I think it is time to take a fresh approach to those questions using these powerful modern tools. I would suggest starting with Loseyourname's excellent question.
loseyourname said:
If physics is the study of what is possible in the physical world, then metaphysics is the study of what is possible for physics. That is, metaphysical questions are very generally of the type: What are the constraints placed on reality above and beyond the constraints of physical law?
Ignoring the relatively unimportant questions of the meaning of 'metaphysics' or how to classify various questions, I think the key question here is, "What is possible for physics?" That is, What are the constraints on reality including those of physical law?
The question of what is possible in the physical world is known to a great extent, thanks to modern science, and that should help us determine what is possible for physics.
Now, even more basic than "What is possible for physics?" is the question, 'What is possible?' Physics may turn out to be just one of many possibilities.
And more basic yet is the question, 'What is?' That is the fundamental ontological question and I think it should be the starting point of our inquiry.
One thing we can learn by studying the works of earlier thinkers is that it is probably a mistake to claim to know anything for certain. Science has given up finding Laws of Nature in favor of finding Theories, which are really guesses at what might be "true" laws. Similarly Mathematics no longer distinguishes between axioms which are obviously "true" and postulates which are simple agreements about starting conditions; they make no claims at all concerning truth. And, the theorems are not considered to be truths but simply tautologies: just another way of stating the arbitrary starting conditions.
So let me sketch out an approach which might shed some light on Euphoriet's questions. We start with the most basic question, 'What is?' and acknowledge that we can do little more than guess. The most certain knowledge we have about what is, or what exists, is that thought exists. Actually we can be pretty sure that thought happens, since it seems to change. Next, we can define 'mind' to be whatever is responsible for these thoughts in whatever manner it is responsible. We have no idea about what sort of thing or entity mind actually is, but we simply take the word 'mind' as a symbol to represent the producer, or container, or agent that makes thought happen.
Moving on, with somewhat less certainty about our guesses, we seem to know that certain thoughts can make up ideas which are more or less consistent and repeatable. Many ideas, such as the notion of an apple, or a triangle, are available to thought at will. This experience of recalling ideas at will not only gives us evidence that ideas exist, in addition to thoughts, but that the capability of will also exists.
The relationships among what I have called 'mind', 'thought', 'ideas', and 'will' are not exactly clear, but it is pretty clear that we can use our minds to think about specific ideas at will. Euphoriet mentioned generating memories "time after time" which suggests that the ideas or thoughts might have a separate sort of existence from mind: The Platonic World.
Moving on with even less certainty, we experience thoughts and ideas that indicate the presence of a physical world. In fact, these experiences are so prevalent that to many people, it seems that such a physical world is all that really exists. The notions of mind, thought, will, and ideas seem to these people less "real" or substantial than the physical world.
Instead of debating the question here of which of these is "more real", let's continue in our mode of guessing and consider the possibility that all of these entities I have mentioned so far, that all of them exist. So at this point, our best guess as to "What is?" is that mind, thought, ideas, will, and the physical world all exist.
The next question is how dependent or independent are these things? Monists would claim that only one of these really exists and that the others are derivative from that one. Dualists would claim that two of them, typically mind and physicality, exist separately. I have recently become what you might call a 'Treblist' since I think the best guess is that there are three separate types of existence, each dependent on one of the others as suggested by Roger Penrose in a couple of his books.
In this view we have Mind, Ideas, and Physicality as separate but interdependent types of existence. It is pretty clear that Ideas can exist in the mind as thoughts, and they can exist in physical form as paragraphs or images. It is tempting to place Ideas in either or both of these places and accept mind-body dualism, but I think such a leap is premature. I'll stick to treblism for the moment. The pairwise dependencies of these three, then, are:
1. Physicality can give rise to Mind via the complex physical brain.
2. Mind can give rise to Ideas via the processes of will, thought, and memory.
3. Ideas can give rise to Physicality (it seems) via Laws of Physics and initial conditions.
(Penrose presents a diagram of these dependencies highlighting the observation that it is only a tiny fraction of each that gives rise to the entirety of the next. I.e. brains are but a tiny fraction of the physical universe; cogent ideas are but a tiny fraction of all thoughts; and the laws of physics and the universal initial conditions are but a tiny fraction of all cogent ideas.)
Of these dependencies, number 3 seems to be the most dubious even though Physicalists must accept such a notion if the physical world is all that exists and that it somehow came into existence from some sort of initial conditions while obeying some physical laws. Regardless of whether that view is correct, it is clear that physical laws and initial conditions are nothing more than ideas.
So, to summarize, my guess as to "What is?": I guess it is the treble existence of Mind, Ideas, and Physicality.
Next, we look at the question, "What is possible?" For starters, it seems that Mind, Ideas, and Physicality are all possible. Since they all seem to exist, it seems unlikely that any of them is impossible.
We could ask, What, if anything, is possible in addition to, or beyond these three? Well, there seems to be strong evidence for multiple Minds. I think most people would agree that there are. There could also be minds that are quite different from the one we are familiar with. There could also be multiple physical universes some of which also might be very different from the one we experience. Some people think there are such universes. And, there seems to be no limit on the varieties of ideas that can exist.
But since we are looking for constraints, let me try to narrow down the possibilities with yet more guesses. One possibility, as Canute has been suggesting, is that the law of non-contradiction might not be hard and fast. That is, it might be possible that something or other might both be and not be. If that were a possibility then reality would consist of two parts: a consistent part in which the law of non-contradiction holds and an inconsistent part in which it doesn't hold.
To make a long story short(er) I'll make the claim that consistency implies the laws of physics. I think Emmy Noether's Theorem suggests this, and I think Dr. Dick has proved it. Thus any physicality arising from consistent ideas will exhibit the properties we see in the physical universe.
So, to address Loseyourname's question, "What is possible for physics?", I would say that if the physical world is consistent, then it must obey the laws of physics as we know them. If it is inconsistent, then all bets are off and it could be just about anything.
Finally, to address Euphoriet's questions, I would say that there is only one Mind and that that Mind existed prior to anything else. I think that Penrose's loop of the three "worlds" does not close on itself but instead constructs a helix. That is, the original Mind constructed a Platonic World of Ideas. A subset of those Ideas constructed a physical world. Then, rather than the physical world creating the Mind (as Penrose's diagram suggests and as most scientists believe), a subset of the physical world (brains) provided a vehicle for Mind in order to construct the next level of Ideas. These in turn produced more complex Physical Worlds with brains, etc.
By now the helix may have made one complete turn, or 50 turns or 50 trillion turns. (My guess is closer to 11 turns.) I suspect that the substrate for the memory Euphoriet asked about, which I think is equivalent to the Platonic World of Ideas, is a structure in the Physical World of the previous turn of the helix. Thus, in the view of Teilhard de Chardin, (and maybe even Frank Tipler's) when our physical universe reaches its Omega Point, it will essentially be a huge computer in which all the information and knowledge of the history of our Physical World's evolution will be stored and available for Mind to use to construct the next iteration of Physical World(s). Just a guess.
BTW, I see nothing whatsoever in this picture of reality that is infinite, perfect, complete, omnipotent, omniscient, or immutable. Since these are all universally claimed attributes of God, I see no place for God as such in reality. Instead, the Mind is us.
Paul