think one must ultimately arrive at some sort of fundamental level of reality, and it is likely necessary. One of my troubles has been seeing why matter itself cannot be necessary.
I will share with you one reason I think matter is not necessary. I will begin with a clear case of something material that is not necessary. Then I will propose how one may infer from this clear case that all matter alike isn't necessary. I will wrap up with a note about why one might think that, even if matter were necessary, the deepest explanation of reality would lack the arbitrary features that matter seems to have.
One way to extend sight is to begin with what is already clear. Here is something that seems clear to me: an ice-cube could melt. I've seen it happen! So, it's clear to me that it could happen. (Note: I don't claim that what is clear to me must be clear to everyone else.) From this clear starting point, I infer something about the material configuration of an ice-cube: the configuration of an ice-cube is not necessary. No ice has necessary existence.
I will soon show why I think that if ice is not necessary, neither is any other material reality. But first, I will offer a tool to help us extend our vision of what is possible in general. I call the tool "modal continuity." This tool gets its power from the observation that certain differences are irrelevant to mere possibility. For example, there could be any number of ice-cubes in a pile. While I have never seen a pile of 1 million ice-cubes, I can see that a million ice-cubes could, in principle, pile together. Differences in number of cubes are irrelevant to mere possibility. Thus, with modal continuity in hand, I infer a pile of ice cubes could be any size.
Here are a few other differences that seem to me completely irrelevant: shape, mass, and number of parts (at least in some possible reality). I infer that an ice pile could, in principle, have any size, shape, mass, and number of parts.
Now to be clear, I do not claim this "modal continuity" tool has infinite power to give you vision of all possibilities, or that it is 100% reliable in all domains. It is a light that can help reveal a line along a dimension of possibility space.
It is now time to use our modal tool to test whether matter is necessary.
To begin, imagine any mountain with any shape and any height. Now imagine a slightly larger mountain. If the first imagination is possible, then so is the second. The change in size is plainly irrelevant to mere possibilty. The very edges in your mind mark a boundary between one possible mound and another.
We can apply this same reasoning to the whole universe. Imagine a big blob that contains all matter in the universe at all times. This blob has arbitrary features, like a certain mass, shape, size, number of dimensions (including a temporal dimension). Must reality contain a blob with those features?
Here's something I think we can know for sure: the blob is not a giant ice-cube full of nothing but ice. Your hands are not ice. So the blob has a different total structure. We can infer, then, that a completely icy universe is not itself necessary.
Why does it matter that an icy universe is not necessary? It is because an icy universe does not appear to differ from our universe in a way that is relevant to mere possibility. If an icy universe is not necessary, then neither is a fiery, dusty, arbitrarily scattered, or odd-number-of-particles universe. These differences in size, shape, and pattern appear irrelevant to a difference in mere possibility.
By the light of modal continuity, we can extend our vision of possibilities along a line of arbitrary features of the material blob. None are necessary. So, by the light of irrelevant differences, all material realities are possibly non-existent. None are absolutely necessary.
I will now address a possible objection. Someone might reply that the foundational material layer (composed of particles, fields, or superstrings) sets the modal limits, like a speed limit sign. For example, if there are exactly an odd number of fundamental particles, then it would be impossible to make the material blob have instead an even number.
This reply, like most replies, helps increase our vision through a cloud of ideas. We need to separate two types of possibility. One type is about what could happen given the existence of our world. The other, more fundamental type, is about what could have existed in any logically possible alternative reality. While it may be true that our material blob couldn't have a different number of particles, it would be a mistake to infer that there could not therefore be a different total blob.
In fact, we have a tool to extend our modal vision beyond the actual world. By the tool of modal continuity, I think we can see that oddness or evenness of particles is plainly irrelevant to possibility (in the most fundamental sense of possibility). Same for shape, size, and mass of any total material floor. They are modally uniform: none are necessary.
Again to be clear, some possibilities may depend upon a completely different universe. Maybe in our universe, mountains can only reach some highest height. But that doesn't mean higher heights are impossible in other possible universes.
Logic doesn't limit the height of a mountain. No mountain top touches the logical limit. All heights are equally consistent with logic (i.e., logically possible).
I work out this idea in more detail in my chapter, "Foundation of Reason," in How Reason Can Lead to God. There I show why I think the foundational layer would contain the laws of logic within its nature, making it as sturdy—as necessary—as the laws of logic. This foundation then provides an ultimate explanation for both the actual and the logically possible.
For the sake of modesty and carefulness, I offer another, independent method to investigate the nature of the foundation of existence. This method is about finding the deepest explanation.
Here is how it works. In general, the best explanation is more probable than absolutely no explanation. So, is there a deeper explanation available of the material world? Is it even conceivable that the material world could be explained in terms of something that doesn't have arbitrary limits, like size or shape or mass or internal scatter? If so, then that deeper explanation would be a better explanation than absolutely no explanation. In other words, even if the material world were somehow necessary, it would not thereby be the deepest explanation of reality. It seems to me that the deepest, least arbitrary explanation would be simpler and more unified than any pattern of particles, strings, or fields appear to be.
I have a book coming out on the foundation of existence (now available for pre-order). In this book, I explain why I think the foundation of existence would have resources to explain every dimension of reality, including minds, matter, morals, mathematics, and reason itself.