Dear Pat, I really do appreciate your taking the time to respond to my efforts. I cannot feel comfortable about my understanding of these matters if I cannot pin down the basis of my inability to communicate with you. Although I am sure neither of us wants to get sucked into another interminable dialog, still I would like to enlarge my comprehension by trying to respond to your points. About "deductive reduction", I had also originally believed that it was equivalent to entailment, but expressed from the other end, i.e., from top down rather than bottom up. But then I thought I saw that Aaron meant something different here, namely the fact that e.g. a computer program does not reveal how it is to be implemented at the physical level, nor do the rules of chess say anything about their physical implementation. So these "architectures" are somehow floating in another realm of reality: they are not bound into any particular implementation. But the "entailment" that I am talking is another sort of connection: it IS "deductive implication" , within some logical framework that must of course be specified. In the present context this logical framework is classical physical theory, which is assumed for the purpose of the discussion of this mind-body problem to provide a (suffiently) accurate description of certain "physical" aspects of the world. Entailment refers here to the deductive implication *from* the facts about the world that are represented in the classical physical theoretical conception of the world *to* facts about the world that are represented or described in some other language, or in some other level or kind of description. My example was the way that---insofar as the description of nature provided by classical physical theory is accurate---the facts of a meteorological description of a hurricane in terms of pressures, temperatures, wind velocities, humidities etc. are entailed by the facts of the classical physical description. Regarding "possible worlds" versus "formal systems" in the context of the meaning of entailment it must be mentioned that the notion of "laws of nature" enter into our idea and characterization of "possible worlds", and the entailments can depend on what these laws are. The present discussion revolves around the distinction between the "true laws and nature" of the world, whatever that might be, and the putative laws and nature of the world proposed in classical physical theory, and the deficiency that I claim for the latter for dealing with the connection between brains and the experiences associated with them. About my description of what I think is the orthodox classical viewpoint you exclaim: "This is physics?? If so then physics had better get its act together. Its not neuroscience or psychology, both of which assume that experiences have causal effects on the physical world". I agree completely that physics had better get its act together, in the sense that this orthodox classical conception is not the right kind of physical theory to serve as a foundation for psychology or neuroscience, if these disciplines want to examine the connection of brains to the experiences associated with them. Indeed, that is exactly the point that I have been trying to make. I now have your reply to Gregg . At the end of you make one point very clear: "Of course the physical facts do not entail the phenomenal facts without additional bridging laws. My point is only that it applies just as forcibly to *any* facts that are not couched in the particle-field language of physics." About these additional bridging laws, which we agree are needed, I have never said that they are "invalid", as you claimed. I have only repeatedly said that the principles of classical physical theory---and the classical micro-physical description of the world that classical theory says exists--- do not, by themselves, entail the existence of phenomenal realities associated with the body/brains of normally behaving human beings, although this classical description does entail their (overt) behaviours. I guess we now agree on this main point! But this conclusion immediately entails that zombies are logically possible within the framework of classical physical theory, and that having experience is not necessary for normal human behaviour: experience is epiphenomal. I regard that as a serious defect of the classical theory, and have therefore been urging that we look for a better physical theory; one in which experiences are essential and causally effective. [I do not go here into the great merit in this context of the quantum mechanical conception of nature. But the main point is that in QM the connection between the geometrical and experiential aspects of nature lies at the dynamical heart of the theory, rather than being something that needs to be added on via an added "bridging principle".] Some comparison to biology is in order. You say that physics does not entail biology. That may or may not be true: I shall consider that question presently. But whether it does or does not does not enter into my argument, which is simply that the classical physical theory does not entail the existence of consciousness, and also renders consciousness causally inert, and hence a better theory is needed. A better theory may also be needed as the basis of biology: indeed I think quantum theory will, for other reasons, be needed also there. But I have not made that stronger claim. Actually, there is in your focus on "language" the suggestion that the problem is with our language, rather than with the basic physics. Indeed, if there were a comparable problem of entailment also for biology, then my argument that the problem indicates a need to turn to quantum mechanics--- because quantum mechanics can naturally bring consciousness into the dynamics---loses its bite. I would therefore like to explain why I think there is no comparable "bridging problem" for biology. Biology is a theory, and as such it exist primarily in the thoughts of biologists. To the extent that we are talking about biology merely as a conglomeration of experiences (primarily) of biologists I am certainly making no claim that its existence is entailed by the classical physical description of nature: that would run counter to my main claim about experience. But there are what might be called biological physical features of nature that are akin to the meteorological facts about hurricanes, in that---to the extent that classical physical theory gives an adequate description of the physical aspects of the world---these features are *entailed* by the classical physical description of the world. But then I must explain how I make this separation of biology: it would certainly seem at first sight that one can hardly separate the physical and experiential aspects of biology, since, for example, one cannot even talk about "cells" without a theory, and it would seem that the biological concept of a "cell", which is pretty basic to biology, is not "entailed" by purely physical theory. My answer, in brief, is that some biological features of nature can be incorporated into the classical physical theoretical description in essentially the same way that certain meteorological features can: there is no need to introduce an extra bridging principle comparable to the one needed to link consciousness to brains. The key to this separation is the point that I have repeatedly emphasized before, namely the essential role---identified by Einstein and Bohr---of the readings on measuring devices, and certain generalizations of such readings. Classical physical theory is a theory, and as such it exists in the realms of experiences of scientists (and philosophers). These realms of experience contain not only these conceptual elements also experiences that a scientist might call "experiences about the physical world coming via their senses". Classical physical theory is based upon certain correspondences that exists between these two kinds of experience, which we can call physical/theoretical and physical/empirical respectively. The physical/theoretical concepts were constructed as generalizations of the physical/empirical experiences, so the two classes of experiences are of the same general kind, and hence can be compared. The point at which the comparision between the facts of the physical/theoretical conceptualization and the physical/empirical experience is cleanest is the reading on a physical measuring device: the fact that some measuring device is, according to the physical/theoretical description, displaying the number "8" and that you are empirically experiencing the display of the number "8" on this device is an example of clean matching between the two pertinent parts of your experience. In the case of the hurricane the readings on devices that measure temperature, pressure, wind velocities, humidities, etc., can be deduced from the classical physical theoretical description of the world, which specifies, in principle, the locations of all the particles and the values of all the fields at all times, and hence the spacetime forms that constitutes the displayed readings on the measuring devices. Over a period of time the communication among scientists allows their empirical experiences to be enhanced and colored by communicated theoretical concepts, expressed in some scientific jargon: they become able to "see" more. They can see "753". and talk about it in some language. These numbers are not the only spacetime configurations of matter that a communicating group of scientists, or other human beings, can come to recognize and communicate: the Japanese and Chinese have a huge variety of strange wiggly forms that are symbols to them of other things, and that they can communicate about. So likewise is it with other form, such as automobiles and horses and cells: groups of communicating persons can learn to recognize clear cases of symbols and other objects that belong to specified classes, and can talk to each other about them. The physical sciences are built on a huge set of classes of such spacetime forms. Gradually, over the course of hundreds of years a huge body of physical/empirical experience of thousands of communicating scientists has been used to form what can be called the classical physical theory of nature. It includes biological facts along with many others. It is organized around the idea that all of our physical/empirical experiences are experiences of objects and systems built out of the particles and fields of the classical physical theory. Physics experiments are explicitly designed so that the results will be expressible as the occurence of one of a set of mutually exclusive recognizable and communicable (to other trained scientists) possibilities. Thus is what allows entailment of results derived from the physical description of some system to the world of physical/empirical experience. Although the particular recognizable and communicable spacetime forms that are used by physicists differ from those used by biologists the general logical situation is the same. The bridging principles used to connect the basic microscopic description in terms of particles and fields into the language employed by physicists for dealing with falling objects and other observable physical systems is not essentially different from how biologist connect that physics to biological systems: the basic procedure is the same. Spacetime forms deduced from the theoretical description are compare to recognizable and communicable forms that constitute the symbolic basis of the discipline. Entailment between levels is allowed because the symbols in each discipline correspond to forms that constrain the parameters of the basic micro-physical description. It is useful, now, to distinguish "vertical bridging principles" from "horizontal bridging principles". In the classical picture described above there is a conceptualization of the physical world and "next to it" the corresponding physical/empirical experiences. For each of us who thinks about these matters there is also an enveloping larger realm of experience that includes these and much more, such as fairy tales, and our relections on this whole picture. If we think of the various physical theories as arranged in a vertical tower, with physics on the bottom, then we may contemplate vertical bridging principles that link, say, physics to biology. On the other hand, there are also the horizontal bridging principles that link, say, our theoretical conception at the physics level to our physical/empirical experiences as this level, and also the similar connections at the biological level. I think that perhaps the difference between your view, Pat, and mine is that you are thinking of adding a theory of phenomena at the top of the tower, necessitating a new vertical bridging principle, whereas I see the bridging between the physical and experiential domains as the horizonal bridgings that are included from the start, in order to tie theory to empirical findings. I have argued that none of is problematic: I see no need for any vertical bridging principles; for the vertical linkage is carried by the physical theory. The horizontal bridgings do involve the entire process process in which a scientific account based on the presumed classical physical material base, and the identification by the scientific community of the symbols for the various disciplines, as descibed above. But the basis of all of these is the same: identification of pertinent recognizable spacetime forms. But as you yourself have stressed, the incorporation of general experiences into this picture of nature based on classical physical theory seems to require special bridging principles: experiences of anger and anxiety, or of towers of unimplemented computer programs are not recognizable as the sorts of spacetime forms that come into our consciousness through our senses, and the conceptualization used above therefore becomes inadequate. Best regards, Henry