The focus of this paper will be on certain aspects of three concepts, those of existence, explanation, and force, together with some related ideas. Specifically, I want to look at some of the roots of those concepts both in written history and, somewhat speculatively, in more primitive circumstances of the history of the human species; and I want to compare certain aspects of the three concepts with their rational descendants in the theories and expectations of contemporary physics. Although these topics are interesting and important in themselves, and there is much more to say about them, my primary aim in the present essay will be to extract some methodological implications from them regarding the problems and methods of the philosophy of science. Indeed, some of the ways in which the topics are important for philosophers of science will be brought out by the discussion of those methodological implications.

Radical Behaviorism makes the implausible claim that “the appeal to mind explains nothing at all” (Skinner 1971, p. 186). Clearly, such a claim (if accepted) would lend strong support to the Skinnerian research program, if only because it would eliminate the major competition. But what support remains when such a claim is not accepted? This paper shall argue that the Skinnerian research program need not depend upon the supposition that there is something scientifically illicit or vacuous about the explanations offered by mentalistic psychology. Distinguishing Radical Behaviorism from a position that grows out of Skinner’s writings from 1938 through 1950, it asserts that the latter position provides a conception of the behavior analytic program that is compatible with the basic claims of cognitive and folk psychology.

We may give a rough definition of this position by following Cummins (1983) in distinguishing between two types of scientific theory.

Over the past two centuries the character of science has changed markedly and crucially. When humans had relatively small amounts of information and energy available they perforce had no option but to attempt to describe objectively a world which behaved independently of them. The basic practical problem was to discover what the pattern of the world was so as to adapt themselves as best they may to it, a little in anticipation of events, but mostly in reaction to them. It is these circumstances which give most sense to the empiricist paradigm of objective knowledge.

But the more information and energy is available to us, the more we are able to ascend from merely correct description of what is to a grasp of what is possible. Newton's laws don't merely describe the paths of the actual projectiles that have fallen and will fall, they describe the paths of all possible projectiles.

My eyes are notoriously bad, so I am not sure whether I have ever seen a meteor. Others have seen them, of course, but it is important to me to observe them first hand. I even go to the trouble to hike at night in the desert mountains so that viewing conditions will be ideal. I scan the sky through my thick glasses, but to no avail. My companions have sighted several, the latest just to the left of that peak. And still I am unsure. Did I really see the meteor, or was it just that my eye twitched? I suspect that this question has no unambiguous answer and that understanding why it lacks such an answer will provide important clues about the role of observation in scientific theorizing.

A central aspect of the computational theory of vision developed by Marr and his coworkers is the use made of contingent regularities in the physical environment to explain how the visual system determines the shape and location of objects in the world on the basis of the spatial organization of the retinal image. Marr (1982) refers to these environmental regularities as “natural constraints” and “physical assumptions.” In this paper I am concerned with recent arguments concerning the implications of this feature of Marr’s theory for understanding psychological explanation. Burge (1986) claims that Marr’s use of natural constraints shows the theory to be nonindividualistic, in the sense that the individuation of psychological states depends essentially on the objects and conditions of the world external to the subject. While it does capture an important aspect of Marr’s theory, Burge’s account is misleadingly incomplete. To see this it is useful to compare the issue of individualism with the question whether the theory is compatible with methodological solipsism as a research strategy.

The Discours de la Méthode and the three essays that were published with it, the Dioptrique, the Météores, and the Géometrie make up a very curious book. The very title page emphasizes the preliminary discourse, and that discourse, the Discours de la Méthode, emphasizes method, the importance that method had for Descartes in making the discoveries he made, the importance that the method Descartes claims to have found will have for the progress of the sciences and for the benefit of humankind as whole. Descartes is not, of course, telling us that we are obligated to follow his method; the Discours is, after all, proposed “as a story, or, if you prefer, as a fable.” (AT VI 4). But Descartes expects that we will all see the light, the light of reason, of course, and follow his example.

Some may find an oxymoron in my title. But, my use of “instrumental” is to focus attention on the real instruments of science-pumps, dynamos and cyclotrons-and not the view that scientific theories are best understood as instruments. In what follows I characterize and argue for a kind of realism strongly wedded to what we do with scientific instruments, and divorced from what our theories may say about the entities manipulated by these instruments. My discussion owes much to Ian Hacking’s “Experimental Argument for Realism” (Hacking 1983, ch. 16).

The following fantasy might help give some idea of the view I am interested in. Suppose that the diskettes, which many people use in conjunction with a small computer, do not store information magnetically; in fact they store it “radioactively,” exactly how, is not relevant. IBM decided that many people in their target personal computer market would be put off by “nuclear diskettes.”

Mathematics plays a central role in the description, explanation and manipulation of natural phenomena. To what extent, and how and why mathematics applies to nature is a problem that has long occupied philosophers. Descartes, Leibniz, Kant, Mach and Poincaré, to mention some of the most distinguished names, offer global solutions to this problem that are based on deep-lying metaphysical assumptions. In this essay, I would like to suggest an alternative approach, which is piecemeal rather than global, and historical before it is metaphysical.

I want to propose, first, that the question of applied mathematics be recast as a question about how mathematics and physics, a physics “always already” mathematized, are partially unified at various points in history, in such a way that they can share certain items, problems and methods while nonetheless remaining quite distinct. And, second, I suggest that these unifications may be quite heterogeneous and variable over time.

It is difficult to determine the place of experience in Descartes’ philosophy and science. His a priori, rationalist metaphysics would seem, on the face of it, difficult to reconcile with the explicit appeal he makes to sensory evidence in both his scientific practice and methodological remarks. Although earlier descriptions of Descartes as a pure a priorist in natural science (e.g., Koyré 1978, pp. 89-94) have rightly been rejected, it would be a mistake to embrace the other extreme, as does Clarke (1982), with his bold revisionist thesis that Descartes was, in actuality, an empiricist. And yet the possibility of combining the rationalist and empiricist elements in Descartes’ thought has also seemed problematic, for it has been assumed that Descartes required that experientially based knowledge meet the standard of absolute certainty set by the the method of doubt in the First Meditation (Garber 1978).

Van Fraassen stresses two distinct but interrelated themes in The Scientific Image: the semantic view of theories and the epistemic status of unobservables. The first of these could easily be accepted by a scientific realist, and indeed realists like Giere have already adapted it to their purposes. So the specifically empiricist thread in van Fraassen’s philosophy stems from the second.

Van Fraassen breaks from tradition in founding his empiricism not on the ontological status of unobservable entities but on the epistemic attitude we take to them. The main points of his position are these:

1. 1) The claims of scientific theories, including claims about unobservable entities, are to be taken literally. Theories are not reconstructed so as to remove claims of the existence of unobservable objects.

2. 2) Observation is a matter of direct observation by accepted participants in the human scientific community.

The ability to observe is the ability to reliably detect, but that is not all observation is. A thermometer reliably detects temperature yet does not observe the temperature, whereas I do, even though in terms of reliability I cannot match the thermometer. An observation is detection accompanied by active classification and, typically, the subsequent formation of opinion. Even when we say of an animal that it can see something we mean more than that it reliably detects things of a certain sort but also that it deals with such things as objects, gauging their usefulness or lack thereof in relation to its interests and to other aspects of the world. This crucial addendum to the notion of observation can be enshrined in slogan: observers are potential believers. This marks the difference between mere detecting mechanisms and observers.

The contemporary scientific anti-realism of one such as van Fraassen, which is developed in detail under the label of “constructive empiricism” in van Fraassen (1980), can be characterized in terms of detecting mechanisms.

In this paper I discuss how, given the complexity of biological systems, reliance on theoretical models in the development and testing of biological theories leads to anti-realism. This is the result of the uniqueness and hence diversity of biological phenomena, in contrast with the uniformity of items in the domain of physics. I have argued elsewhere (Horan, 1986, 1989a, 1989b) that the use of theoretical models creates an unresolvable tension between the explanatory strength and predictive power of hypotheses, and I review this argument here. My discussion is in part motivated by the claims of Nancy Cartwright (1983), who has argued that the use of ceteris paribus laws in physics creates an antagonism between truth and explanation that requires theoretical models to figure centrally in scientific explanation, thereby precluding realism. I argue instead that in biology it is the use of theoretical models that creates this conflict, and conclude that adequate biological explanation cannot rely on the modelling approach alone.

In “A Confutation of Convergent Realism,” Larry Laudan presents the realist with these fascinating challenges:

Not only do I fully endorse what Laudan says in these passages, I think it is time to take him up on these challenges.

Laudan’s position has been that scientific progress can be explained without having to appeal to verisimilitude. Instead, we explain the success of a scientific theory in terms of its subjugation to the cannons of experimental controls: those theories that have been put through proper testing during the course of their formulation are the ones that are most likely to be reliable. (1984, pp. 96-101)

The semantic view of theory structure, as developed by Suppes (1957,1967), Suppe (1974, 1976, 1977, 1988), and van Fraassen (1970, 1972, 1980), represents theories as classes of models or structures. These models are, on the version of the semantic approach used here, defined by specifying their laws, parameters, and variables. The semantic approach to theory structure is simply a method of formalizing the content of scientific theories.

In a series of articles and a book, I have analyzed the structure of modern evolutionary theory using the semantic view as a framework (Lloyd 1984, 1986a, 1986b, 1987a, 1987b, 1988, forthcoming; cf. Thompson 1983, 1985, 1988). I shall briefly recap the analyses I have done, in order to demonstrate the range of problems accessible to the semantic view.

First, I have used the semantic view to analyze the structure of population genetics models, including kin and group selection models.

Over the last eighteen years Manfred Eigen and his co-workers have postulated a new theory about the origin of life on earth that has presented a detailed account of how many of the features of extant living organisms (such as a universal genetic code and protein-nucleic acid interdependence) might have arisen from purely physical interactions.2 This theory is critically based on the special dynamical properties of certain chemical cycles called “hypercycles” which cause some of them to exhibit hyperbolic growth over time while undergoing selection. The purpose of this paper is to separate two aspects of this theory and then to study the first one in greater detail. The first aspect consists of a physical account of evolution by natural selection at the molecular level that depends only on the kinetics of certain chemical systems and can be applied to a variety of such systems. The second consists of the special dynamical properties that are exhibited when this account is applied, specifically, to hypercycles.

The semantic conception of theories has a relatively short history the beginnings of which Frederick Suppe has traced to von Neumann (Suppe 1988). Two other early initiators and advocates were Evert Beth in 1948-49 (Beth 1948, 1949; see also 1961) and Patrick Suppes in 1957 in his Introduction to Logic (Suppes, 1957). Beth advanced what has become known as a state space approach while Suppes advanced a set-theoretical predicate approach.

Suppes suggested that scientific theories are more appropriately formalized as set-theoretical predicates. Shortly thereafter in 1961 Robert Stoll in his Set Theory and Logic (Stoll, 1961) made a similar claim about the formalization of informal theories of which scientific theories are instances. Suppes wrote a number of papers during the 1960's in which he indicated the features of theories that were better represented on a set-theoretical predicate conception of theories (see, for example Suppes, 1962).

Sustained controversy over a philosophical issue is often times symptomatic of differing commitments at a more fundamental philosophical level. I will argue that two current debates over the foundations of the theory of natural selection are cases in point. Alexander Rosenberg, at times together with Mary Williams, challenges what is becoming received orthodoxy about the foundations of this theory. He argues that the currently popular propensity interpretation of fitness does not legitimize explanations in terms of natural selection, and that furthermore, the biological fields which typically study the ways in which selection pressures originate in the organism/environment complex are not in fact part of the theory of natural selection at all. His foils in the first case are Robert Brandon, John Beatty and Susan Mills;2 on the second issue he is engaged in debate with Elliott Sober.3 We will see that, although the controversies are ostensibly about the interpretation of fitness, the issues, at bottom, involve the nature of scientific explanation.

Two attitudes largely dominate current philosophic thinking about the social sciences. One argues that the social science are not and cannot be real sciences—because the social sciences have not and probably cannot produce anything like the laws of the natural sciences. The other attitude—coming from the hermeneutic tradition—defends the social sciences, but only by arguing that laws are irrelevant to social explanation. Disparate as they are, both traditions share the assumption that laws in the social sciences are beyond reach. In this paper I argue the opposite thesis—viz. that social laws are both a possibility and actuality.

Philosophers have typically approached laws in the social sciences by an old-fashioned route—by means of relatively a priori conceptual analysis. One or several necessary conditions for laws are identified, usually by appeal to intuitions. Then it is argued that no alleged law in the social sciences could have the necessary features.

The issue of whether species are individuals is now an old one; the literature abounds with arguments, counter-arguments and counter-counter-arguments for their individuality. The question I want to take up in this paper is not whether species are indeed individuals, but what ramifications their alleged individuality has for macroevolutionary theory.

According to those biologists who argue for a new theory of macroevolution, the individuality of species is one of the fundamental premises of that theory. For example, Joel Cracraft writes of himself and others that

Explicit or implicit ceteris paribus clauses are pervasive in economics. People do not always buy more of x when the price of x decreases. The generalization holds only “other things being equal” or ceteris paribus. Not everybody wants more wealth, but economists have held that the generalization holds, ceteris paribus. When government imposes price controls, shortages do not always arise, but, ceteris paribus, they do. Ceteris paribus clauses are common in other sciences, but I shall confine my remarks to economics.

Many have found such ceteris paribus clauses problematic. For they are vague, and they seem to insulate theories from empirical criticism and correction. When the observed phenomena are not as the theory predicted, one can (or so it has been alleged) always claim that other things were not “equal”, that there was some “disturbance” or “interference” and thus that the ceteris paribus condition was not met.