Therefore I offer up the first thesis:
(1.1) Our conception of the material world affords a model of experience.Notice immediately that (1.1) does not describe the material world itself, but only our `conception' thereof. The term `model of experience' may seem somewhat obscure, however, and will require a definition of its own, and which I shall provide in thesis (1.2), after exploring several examples. Its use is motivated by the notion of a scientific model, especially in physics, in which a scientist or mathematician represents some presumably real system by a set of rules and relationships which he explicitly determines.
A model of experience, then, is a conceptual framework for relating together our experiences. For example, suppose we're watching a group of roofers repair a housetop, and we see that one of them accidentally drops a shingle over the edge. As the shingle begins to fall to the ground, we understand, based on our conception of how matter behaves, that the shingle will continue to fall, relatively straight down, and come to rest on the grass below. This knowledge gives us an idea of what visual experiences to expect. We can predict all sorts of experiences with the model we have in our conception of the physical world. Suppose again that some person, call him John, is outdoors among a group of baseball enthusiasts, and they have invited him to play a game of catch. He accepts the invitation, and one of the players throws a baseball towards him. He sees the ball fly fast and straight in his direction. With his conception of the physical world, he can predict that, unless he takes action, he will experience an unpleasant sensation of the ball striking him hard somewhere on his body. As the ball comes closer, if he pays close attention, then his expectation of where exactly on his body the ball will strike---and therefore what experience he will have as a result---increases in accuracy. At the last moment, he may come to expect the ball to hit him squarely on the nose! He gleans this expectation of experience from his conception of the physical world. In this way, his conception of that world affords to him a model of experience.
Of course, we do not necessarily require that our conception of the physical world is not something more than just a model of experience. Materialists, for example, may assert that there lay something beyond our ideas of matter which is somehow represented by those ideas. So, for these representationalists, a person's conception of the material world is also a kind of mental image of something real. Yet even on this view, his conception still also provides him with a model of experience. Indeed, whatever else it is, it seems difficult to deny that it is at least such a model. Still, some may resist this conclusion by suggesting that, instead of affording a model of experience on its own, our conception of the physical world merely is one tool among many for constructing a model of experience, useless to the task without those other supposed components. In response to this potential objection we need only point out that by `conception of' the material world, we mean to include our understanding of how to relate the world to our experiences. This, it seems to me, is quite sufficient to capture the examples given previously.
To continue to explore what we mean in (1.1), let us consider another model of experience, in particular, a social model: We all, hopefully, have a basic understanding of social etiquette, and this allows us to come to expect certain experiences given recognizable social conditions. For example, if we are having a conversation with a friend, and we blurt out a random expletive, our conception of social interactions tells us something about what we can expect in response, namely an expression of simultaneous dismay and curiosity at our unusual and rude behavior. Similarly, certain hand gestures we understand to elicit various types of responses on the part of our fellow social players, and in this way we can use our conception of social structures to predict and control our experiences. In other words, that conception provides us with another model of experience.
Now, this example of a social model isn't completely divorced from the physical model, because we understand our social interactions as taking place, in some sense, in the physical world. However, this doesn't mean that they are the same model, but only that they share some (though not all) of the same elements. Consider one difference in particular: in the social model, we use the states of mind of other people in order to predict their responses. While some may believe that the mind is reducible in principle to physical operations of the brain, that is not how we currently understand mental states. Regardless of what is possible in principle, the fact remains that in actuality, we do not reduce mental states to physical states, if for no other reason that we don't know how to do so at the present time. Perhaps in the future we will combine our physical and social models, but for the time being, they are quite different, neither one reduced (as opposed to reducable) to the other, nor both reduced to any other more basic model. So, we can see that these models of experience are indeed quite different from one another, though there may be significant overlap.
However, it is possible to find a purely mental model by attending to one's private thoughts. For example, we have all (hopefully) developed mental exercises which we use to memorize important facts. These exercises may include performing mental repetition, constructing cute acronyms, linking new information with old information which has already been memorized, or incorporating mundane facts into a richly interesting narrative, just to name a few strategies. While we may augment these mental strategies with physical strategies, they are nevertheless themselves strictly mental. It is, therefore, our conception of how our own mind works which tells us what to expect if we engage in such mental exercises. In other words, our conception of the workings of our own mind is yet another model of experience.
So it is that we can find physical models, mental models, and models which incorporate both physical and mental elements. We have seen that models can overlap, or share elements. Now let us observe that it is also possible to find narrower models wholly within other, larger models. For example, we can use classical mechanics to create scientific models of the physical world, and so they are also models of experience insofar as knowing about the physical world helps us anticipate experience. However, clearly we understand the physical world through other means besides classical mechanics. Recall, for instance, the roofer we considered earlier, who drops a shingle from the housetop; we are not actually performing mathematical calculations to determine what will happen to that shingle! We know based on what you might call a folk understanding of physics that the shingle will fall to the ground. Perhaps we could have used classical mechanics given sufficient motivation and preparation, but we by no means need to always appeal to Newton's formulas to predict our experiences with the physical world. On the other hand, with the tools of classical mechanics, we can construct very accurate and models of experience given certain conditions. We can choose, as the occasion demands, to treat these models as either individual and self-contained, or else a mere part or ingredient of a larger, broader-scoped model. In this way, our discussions of various models will depend in some respect on context.
With the preceding examples I have attempted to provide an intuitive notion of what constitutes a `model of experience.' With these in mind, we can introduce a more rigorous definition:
(1.2) A model of experience is any conceptual system completely characterized by a collection of imagined experiences along with their assumed regularities.For clarification, we do not require that a model be deterministic. It could be, for instance, that, given some set of initial conditions, instead of prescribing definite outcome, a model will only predict a certain range of possible experiences. Furthermore, notice that, lest we suspect otherwise, models of experience are not, as a phenomenalist might wish to say, just sets of counterfactuals, though they certainly have the potential help us make sense of them. Rather, models are self-contained systems of assigned relationships between imagined experiences. Finally, since models are `completely characterized' by those objects and their regularities, we have a clearer idea of what we mean by having some conception `afford' a model; in particular, we need only strip that conception of all its non-characteristic (in the sense of (1.2)) parts, and, voici notre modèle! In this way, we can---and indeed have already, to some limited extent---for the sake of simplicity, speak of the physical world as actually being a model of experience, instead of merely affording one, since its identity beyond its characterization as a model we may consider unimportant in certain contexts. So we see how (1.2) captures the spirit of the several examples listed thus far, and indeed how it illuminates that thesis asserted in (1.1).
Our conception of the physical world, then, whatever else it may or may not be, certainly serves as an indispensable model of experience, as affirmed in thesis (1.1). Later on, I may argue that, despite the linguistic hinting by the phrase `of the material world,' there is not really any realm of existence beyond our ideas which that conception represents. I may also suggest that the models themselves help to generate our experiences, such that the objects of experience can sometimes be objects in the model which we perceive through our understanding of that model. However, neither of these conclusions are at all required to accept (1.1) and (1.2), which tell us little more than that our conception is a tool for predicting and controlling experiences, a fairly straightforward and uncontroversial position.