Sara Leanne Mastros Physics and the Physicalist Dr. Barbara Montero Ver 1.2.hard Ver 1.2.3.soft copy at www.ugcs.caltech.edu/~abszero/phys-philo.txt Every naturalist , at some point in her thoughts, if not in her writing, makes a last ditch appeal to physics to provide a working ontology. "Those objects exist," she says, "which physics speaks to us of." There is a fatal flaw in this seemingly harmless statement, one that threatens the underpinnings of any rigorous treatment of naturalism which grounds itself in an onotlogy dervied from physics. Physics can never tell us anyhting about the true nature of the world around us, nor does it attempt to. This may seem a radical claim, but it is one I feel follows immediately from an understanding of the nature, goals, and methods of modern physics. To begin, let me propose a standard "physicalist" definition of physics. "Physics is a set of rules which describe the behavior and relation of objects (matter) and causal reactions (forces) with one another in a structure of space-time. " Let us analyze this definiton and see what results. First, physics is a set of rule about relationships. Physics does not make existential claims. However, this problem is easily solved by our physicalist, who reformulates her ontological imperitve as such "an object is physical (and therefore real) iff it can be completely defined by physics." She as now established a judgable criterion for physicality. Now that we have solved that small dillema, let us move on to a bigger one. The proposed definiton of physcis leaves out a crucial pointÑin what way do these rules describe the world? For most of physics history, this was a simple question. Physical laws are causal and deterministic. By "causally deterministic" we mean that, given the complete state of a closed system, we can extrapolate its state at any future time (or, to be technincal, we can extrapolate the system-state between nodal points (such as the big-bang/crunch)). Modern physics is neither causal nor deterministic. When it speaks of objects, moder physics is probabalistic and decidely non-causal. Why would we ever formualte a physics so counter-intuitive? There were several historically motivating factors, including most notably the photo-electric effect. But, there is a mipler reaon why we construct physics the way we do. The confusion about why physics is counter0intuitive boils down to one flaw in logic. We donÕt "discover" physics; we invent it. And we invent what we do because it works. Quantum physics begins with a rasical paradigmatic shift from the classical: objects are not determined. Were Heisenburg to reply to our physcialist, he might be very confused. "How is it, young lady, that you can determine the reality of an object when you cannot determine its position? Is an object not defined by its extension?" "Well, Dr., I understand that we cannot know both the exact postion and momentum of an object, but that hardly means that the object doesnÕt have an exact physical extension. Does it?" Here we might imagine a hearty chuckle form Dr. Heisenburg. "In fact, good woman, it means exactly that. I never said that we cannot know things. What we can and cannot know is well outside my interest. I said that the object DOES NOT HAVE an exact speed nor an exact position. There is not an exact object. You cannot draw conclusions on whether or not things exist based on a theory which specifically says they netiher exist not fail to exist. But, I have a happy surprise for you. I can explain quantum theory in such a way that it causally determines things. IÕm afraid youmight not like it thoughÉ" A fairly new breed of physicist, led perhaps by David Deutch, has reformulated quantum theory in a radical new way. Instead of talign probabalistically about cassical objects, we can speak deterministically about schroedinger-style probability wave-froms. Alas, this seems to leave our poor physicalist at a loss, now not only are tables and chairs not "physcial" but niether are the most basic of elementary particles. Uh-oh. In this formulation, a translation without meanig change from more standard quantum models, we have radically changed what does and does not qualify as physical. In the Deautch formaulation, the only "physical" objects are solution to equatonÑabstract entities in our common sense paradigm. However, perhaps our physicalist plaunges on; ÔAt least physics tells us about the world in purely mathematical terms." Here Dr. heisenberg might hand her over to Kip Thorne, who provided me with the following definition of physics. Physics, like any scientific theory, is a model of the world around us. And, like any science, it is built on assumption, fueled by observaton, and furthered by logic. If we define "the universe" to be "that which is", physics begins with the following assumptions: 1-At least part of the universe is knowable. (the epistemological assumtion) 2-The universe is casually closed. (the ontological assumption) 3-the universe is the way it appears to be. (the empirical assumption) Assumption three is the empircal basis of science, and it lies at the core of all contemporary (post-cartesian) science. In many ways, it IS the key to a cartesian scientific method. Without this assumption (and do not think there is any a posteriori basis for it) science reduces to mathematics, a hollow and impotent game incapabel of conveying information about the world. Physics can only extend the senses; in no way can it supercede them. Assumption three, however, also places physics outside of the validation-space of any ontology. Dr. Brandom would say that it "is not part of the game of asking for and giving reasons" concerning what there is, as it has already made an assumption on this point. There is what there appears to be. Physics cannot tell us what the worls is only better our capactiy to see what it appears to be. There is no priviliged method by which physcis can grant us some peek inside the secrets of the universeÑphysics can only extend our senses. Physics can provide more data to fuel philosophical debate, bt it does not offer a different sort of data than naked observation. Physics is a database of concentrated sense-data. The physicalist dillemma comes down to naturalizing physics befor anythig else. 1- I'll be using the terms "naturalism" and "materialism" interchangably to mean a belief I nonly one sort of object, made form physical, material stuff. Physicalism IÕm reserving specifically for an ontology derived form physics, either present day or "perfected/completed". 2- This appeared to be the definiton we were working with in class. IÕm trying to find someone to site with a simliar definition. 3- Here I donÕt mean contemporary, but rather non-classical, or post-quatnum. 4- IÕll add abot a page explianing this when this weekend. Check the online copy to see the update. IÕm waiting on another emial from Kip. 5-this is a slight modification of a definiton proposed by Kip Thorne.