I was wondering what you think about Sider's objections raised to existence monism (according to Sider, they apply just as well mutatis mutandis to priority monism as you defended it). In particular I'm curious about what you'd say regarding his first objection:
"Consider a world containing just a single computer screen with a 2x2 pixel resolution. Each pixel can be on or off. Since there are 4 pixels, and there are two states for each pixel, 2^4 states are possible for the entire screen. The existence of this statespace is common ground between monists and pluralists. But only the pluralist can give a satisfying account of why the statespace has 2^4 members. The pluralist can say: the statespace has 2^4 members because i) there are 16 pixels, each of which has two available fundamental states; ii) the fundamental states of the system include only the states of the individual pixels; and iii) the possibilities for the entire system are generated combinatorially from the entities in the system and the fundamental states those entities can inhabit. The monist can tell no such story. For the monist, the fundamental properties are the members of the statespace itself: the 2^4 (or 16) maximally specific properties of the entire screen. These properties are not generated combinatorially from more fundamental pixel-properties. Why, then, are there exactly 2^4 of them?" - From "Against Monism".
Sorry, the roman numeral i reason that the pluralist gives should say there are 4 pixels (I changed the math from the original to make it simpler).
There is a really good and short paper called "Monism and statespace: a reply to Sider" by David M. Cornell. It not only counters the objection made by Sider, it further attacks Sider's "intuitive" position. In the paper, Cornell explains each of these pixel states is a mode of the screen, i.e. a way the screen can be (a common monist description). There are 10 possible pixel states/modes for a 2x2 resolution screen. Cornell further argues that if a person think of those pixels as separate/independent entities, she cannot account for various notions such as mostly, barely, etc. For example, in a 4x4 resolution screen and 14 of the pixels are on, a monist can say the screen is mostly on. If only 2 of the pixels are on, a monist can say the screen is barely on. Mostly and barely are notions that require you to think of the screen (which is composed of pixels) as a whole. A person who thinks each pixel is a fundamental entity can only tell you how many pixels are on and where they are located. Thus, Sider's position fails to account for those "holistic" properties about the world.
2^4 possible states so 16 instead of 10.
I think that Cornell's response is adequate, but he seems to be missing an important distinction between that kinds of brute facts available to the monist and those available to the pluralist. In a different paper (monism and statespace structure), sider refers to "scientifically ultimate facts". The facts about statespaces in screenworld, for sider, are grounded in scientifically ultimate facts. Namely, facts about photons, or whatever the fundamental physical entities in screenworld are. The monist can't have a completely scientific grounding story, however. Even given the kindness of quantum mechanics to a holistic or monist metaphysics, ultimate facts of a quantum mechanical sort (such as that this point of spacetime takes on field value V) still make reference to sub-world entities (points in a spacetime manifold, vectors in it, and so on). This entities can be metaphysically grounded in distributional properties of the cosmos, as Cornell prefers, but that is what Sider refers to as a "sketchy" grounding story. It is odd that the ultimate facts should be so mysterious as facts researched by metaphysicians, rather than those of fundamental physics.
Your response, on the other hand, doesn't fail to make an important distinction. However, I'm not sure it carries a lot of weight. You probably meant "sider's account fails to explain as well as monism does the fact that we think about whether a screen and its distributional properties before we think of its parts and their individual features". It seems to me more important that an account makes fundamental scientific, rather than abstract metaphysical facts, than that it explains the priority of certain concepts in our minds well. That seems like a job for psychology, not metaphysics.
For example, I don't consider the fact that selves are conceptually prior to thoughts to be a nice point in favor of substance dualism or theism (on which there are souls). It certainly increases their probability, but not by an important amount given the other considerations we have available.
Also I wish there was an edit button, but its a fair trade considering the badass thread UI here!
You brought up some very good points. I have two concerns I would like to raise. First, in general it's not very convincing to say that since fundamental physics says that x and y are fundamental entities, therefore, monism cannot be true or is unlikely to be true. In other words, to claim that x and y are "scientifically ultimate facts" is too strong. The reason is because even physicists disagree on what the fundamental entities are. Nevertheless, you can say since it's at least possible that the fundamental entities are x and y, therefore, in those cases monism would not be able to provide a satisfactory account of the reality.
This brings me to my second point. If you think the fundamental entities are like photons, gravitons, etc. you would have to provide an answer to the gunky universe objection. How do you know that there aren't smaller parts that make up those sub-atomic particles. I think this problem is relatively more worrisome than the objection raised by Sider.
Furthermore, I'm not sure which version of quantum mechanic you are thinking about, but for the Everettian interpretation, those sub-atomic (photons, electrons, etc.) particles are just the wavefunction formed in a certain way at a particular spatiotemporal region. If you believe in field theory, then the sub-atomic particles are different fields formed in a certain way at a particular spatiotemporal region. We perceive photons as spheres is a result of our limitation to detect those entities as the way they really are. All these theories are scientific theories (not metaphysical ones). And I don't think they are mysterious (especially the Everettian interpretation of quantum mechanics). All these theories suggest that our old way of thinking in terms of objecthood is limited in helping us understanding the Natural world. So it's actually opposite to what Sider wants to argue.