In the quantum theory the state of an evolving system is represented by a function that depends on time and perhaps on some other parameters. It is generally called the “psi-function”, and it evolves according to an equation called the Schrödinger equation. Indeed Schrödinger introduced the psi-function into physics. In the beginning (i.e., in 1926) Schrödinger thought that the psi-function referred to a fuzzy bit of reality. That is, he pictured an electron, whose state was given by a certain psi-function, as a pulsating bit of electricity, something like an electrical cloud or a patch of electrical fog. In short order, however, Schrödinger saw difficulties with this interpretation, and after trying out more sophisticated refinements he abandoned the whole project. What he abandoned was the program of trying to interpret the psi-function as directly representing some spatiotemporal features of the object whose state it characterized.

Herbert Feigl was born December 14, 1902 in Reichenberg, Austria, and he died in Minneapolis, Minnesota, on June 1,1988. His wife, Maria, followed him in death on February 13,1989. He is survived by a son, Eric O. Feigl, who is professor of physiology at the University of Washington.

Feigl's parents were Jewish but not religious; indeed, his father was an outspoken atheist. His father was a weaver and later an influential textile manufacturer, who would have preferred the son to become an industrial chemist. His mother was a devotee of the arts and an amateur pianist, who would play Beethoven sonatas over and over at the young son's request. His high school interests were philosophy, science fiction, physics, and chemistry (which was his major). Moritz Schlick became his favorite philosopher after he read the latter's Allgemeine Erkenntnisslehre. His chief intellectual hero was Einstein.

Herbert Feigl was one of the most admirable people I have known. I was fortunate to have him a a friend and as a teacher (he directed my PhD dissertation). He was a very special friend and a very special teacher. To round out what is being said here, I want to share my impressions of him as a teacher and as a person.

I don't think I ever took a course from Herbert; he taught me informally as a thesis director and as a helpful older friend. When he guided me through the writing of my thesis, I was almost unaware fo the teaching he was doing. It is only in recent years that I have come to appreciate how important it was for me.

In comparison with other teachers, Herbert was extremely permissive—the opposite of coercive. For him, nothing was off-limits.

Let's begin with a

Definition: The Anthropic Principle is the drawing of scientific inferences from a consideration of Man's Place in Nature.

There are various versions of the Anthropic Principle. The most conservative version of the Anthropic Principle is nothing but a systematic working out of the fact that the astrophysical (and other scientific) data we have is self-selected due to the fact that Homo sapiens is a particular type of intelligent being. This conservative version of the Anthropic Principle is called the

Again, the Weak Anthropic Principle is just a warning to take into account a grandiose type of selection bias when interpreting data.

Prof. Tipler and his colleague John Barrow, applying the results and methods of contemporary physics, have made a number of suggestions for pushing beyond the limits of science as ordinarily understood, sometimes suggesting that ideas once thought archaic and worthy to be discarded can be revivified in the light of our new theoretical understanding of the world. The role of the observer in quantum mechanics, they suggest, makes at least plausible “idealist” claims of the dependence of matter on mind. Cosmology, they suggest, provides a framework in which the idea of God as evolutionary endpoint of man-in-nature, familiar from Teilhard de Chardin, can be made concrete and plausible at least as a possibility. All of this, admittedly speculative, structure is presented in something like the form of an inverted pyramid, resting at its base on the much less ambitious, if much more secure, methodological posits of the sort grouped together under the (somewhat misleading) rubric of the “Weak Anthropic Principle.”

The “hole argument” shows that spacetime substantivalism leads to a radical form of indeterminism in a broad class of spacetime theories. My purpose in this note is twofold. First I shall present a short and informal version of the argument in the form developed in Earman and Norton (1987). Second I will show how the argument can be extended to the case of “manifold plus further structure” substantivalism whenever that further structure admits certain common symmetries.

The hole argument depends on the possibility of displaying two models of some spacetime theory which agree everywhere but within a small neighborhood of the spacetime manifold. To illustrate how two such models are arrived at, I will describe the construction for the easy to visualize special case of a spatially homogeneous and isotropic expanding universe in general relativity. It will be clear how the construction can be extended to other spacetime theories.

With help from Einstein, John Norton and John Earman (1987; this volume) have invented a fascinating argument against spacetime substantivalism. It gives the philosophy of space and time a refreshing stimulus: all credit to them. The idea of the argument is that substantivalism rules out determinism, even of very weak kinds. Norton and Earman have no special brief to defend determinism. But they believe that if it fails, it should fail for reasons of physics that vary from case to case—it should not fail at a stroke for the sake of a philosophical doctrine such as substantivalism. They conclude that in the conflict between substantivalism and determinism, it is substantivalism that must go.

The conflict arises from ‘hole diffeomorphisms’. These enable us, once we are given a model for a spacetime theory, to produce another model.

The debate over the ontological status of space has been waged over the millennia on many battlefields. In ancient times the major focus was on the possibility of a vacuum, an entity that was both something and yet, in another way, nothing. Newton shifted the scene of action to dynamics, to the question of the ontological commitments needed to give an adequate explanation of observable phenomena. But along with the dynamical effects of Newtonian absolute space came also the spectre of motions unobservable in principle, a notion attacked from Leibniz onward as conceptually absurd or meaningless. So the theater of operation was moved again, especially by verificationists, this time into theories of meaning. Now John Norton and John Earman have opened an entirely new line of assault on the question. They argue that considerations about the possibility of determinism have direct implications for the substantivalist-relationist controversy.

Before we, as philosophers, take a look at string theory I want to mention that more than one person has suggested to me that it is still too early for philosophical and foundational studies of string theory. Indeed, the suggestion emphasizes, since string theory is still in the process of development, and its physical and mathematical principles are not completely formulated, there is, in a sense, no theory for the philosopher to analyze. And I must admit that I think there is something to this suggestion. In a sense I hope I will make clear, there does not yet exist a precise mathematical formulation for string theory as there is Hilbert space for (elementary) quantum theory, and Riemann spacetime for general relativity. Because these latter formulations exist, we can ask precise questions, and prove precise theorems about their interpretation.

In this talk, I'd like to explain a little bit about what string theory is, why theoretical physicists are so excited about it, and why I think that it will have a rather profound impact on some of our ideas about the structure of the physical world.

Let me begin by reviewing the way we think about quantum mechanical particles in a relativistic setting. The classical dynamics of the theory is specified by assuming that the action for a given particle trajectory is proportional to the relativistic interval traversed by the particle. If one sets up a canonical formalism with the variable parametrizing the particle trajectory playing the role of time, then one finds that the four-momentum of the particle is constrained, with the constraint just being the relativistic relation between the mass, energy, and three-momentum of a particle. The particle thus lives on a subspace of the full phase space, and one finds that on this subspace, the Hamiltonian for the system vanishes.

In this paper I will present conceptions of state reduction and particle and/or system localization which render these subjects fully compatible with the general requirements of a relativistic, i.e. Lorentz invariant, quantum theory. In the case of state reduction, the concept presented has, in it's main features, been advanced by several investigators in recent years, (Giovannini 1983), (Aharonov and Albert 1984), (Malin 1984), (Dieks 1985). My own contribution to this topic has been to elaborate the concept in question and examine, in some detail, the often counterintuitive but never causally anomalous or internally inconsistent consequences that emerge from taking the concept seriously (Fleming 1985,1986). In the case of particle and system localization, the concepts are more nearly my own and have been pursued by me for some time (Fleming 1964, 1965, 1966) as a way of freeing the subject of localization in relativistic quantum systems from the conceptual problems pointed out by Newton and Wigner (1949) myself (Fleming 1965) and extensively studied by Hegerfeldt et. al. (1974, 1980) and Ruijsenaars (1981).

This note will consist of a single rather elementary remark about the overall Quantum state of the world.

Let me say something at the outset about what this remark is supposed to be good for. It will not support and it will also not raise any doubts about any particular cosmological model. The problems which this remark will turn out to have a bearing on are problems which those models aren't intended to address, problems (about which, however, there has lately been a good deal of speculation) connected with the ‘ultimate beginnings’ of the world; and the remark will merely suggest that those problems need not be worried about; that perhaps, after, there simply aren't genuine problems like that.

The remark is that if any linear Quantum-Mechanical equations of motion happen to be the true and universal equations of motion of the world, then it is consistent with everything we observe, and it is consistent with everything we are even likely to observe, to suppose that the present (and past and future) state of the physical world is the vacuum state.

Philosophical debate on the measurement problem of quantum mechanics has, for the most part, been confined to the non-relativistic version of the theory. Quantizing quantum field theory, or making quantum mechanics relativistic, yields a conceptual framework capable of dealing with the creation and annihilation of an indefinite number of particles in interaction with fields, i.e. quantum systems with an infinite number of degrees of freedom. I want to show that a solution to the standard measurement problem is available if we exploit the properties of the infinite quantum models available in this broader conceptual framework.

There is a qualitative difference between quantum systems with an infinite number of degrees of freedom and quantum systems with a finite number of degrees of freedom. In the infinite case, there exist many unitarily inequivalent irreducible Hilbert space representations of the algebra of observables of the system. In the finite case, there is only one such representation.

The Neglect of Experiment: that is the title of Alan Franklin's (1986). He did not mean to imply that scientists were neglecting experiments, spinning well financed cobwebs of theories while laboratories decayed for lack of funds. He meant that historians and philosophers neglected the experimental side of science. That was true, and is no longer so. Although his title was fine when he was writing, the times have passed it by.

A decade before there had been almost no reflective philosophy of experiment. What little had been published was not seen as writing about experiment—that was not something to write about—but as discussion of the theory/observation distinction, or the impossibility of eliminating a theory by crucial experiment, etc. The even-handed Dictionary of Scientific Biography discreetly cut articles on experimenters and expanded those on theorists. Thaddeus Trenn's (1977) on the experimental discovery of isotopes was poorly received.

Historians and philosophers of science have, of late, found a new common ground. During the 1960s the two fields worked together to answer the general question: “how does one theory supersede another?” — followed immediately by a second query: “Is the process rational?” Historians provided examples from the chronicles of science, and philosophers tested these cases against universal models of change. Together the two helped ground an important avenue of inquiry, and today the best of that work — by Feyerabend, Kuhn, Lakatos, Popper, and others — forms a staple of the philosophy of science.

But despite the best of intentions, in the 1970s the two fields began to pull apart centrifugally. On one side, the philosophers found their concerns concentrated ever more on fundamental issues about meaning and reference, and these seemed to demand idealized histories with simpler structures.

Scientific realism is a doctrine about the relationship of our ideas on the nature of things to the nature of things itself. Part of the doctrine is that there is a nature of things itself. With regard to the rest, Jarrett Leplin has said, “Like the Equal Rights Movement, scientific realism is a majority position whose advocates are so divided as to appear a minority” (Leplin 1984, p. 1). Still, it can be said that what realists would like is that the account of the nature of things provided by science be true and that those things really exist.

Characterized in this way, realism would seem to be a majority position indeed. As Ernst Mach has said of the doctrine,

It was once fashionable to treat realism as an explanatory theory of science. This realism treats the sentences of science, both observational and theoretical, literally: such sentences are true or false as the case may be in some correspondence sense of truth. To this was added the epistemological claims that it was in principle possible to discover whether any given sentence was in fact true or false and that science has been progressive. In view of the fact that theories seemed to have a bad track-record - from the point of view of truth they all seem sooner or later come unstuck - the realist offered a more modest goal for science; producing more approximately true theories. The strategy for defending realism was explanatory. The realist claimed that inference to the best explanation (hereafter cited as IBE) was a standard epistemic tool of the scientist and ought to be available to the philosopher.