A physicist ’s philosophy

Deutsch’s The Beginning of Infinity (2011) is resolutely and inspiringly opti-mistic about the potential for growth in scientific knowledge, and in conse-quence about the capacity of people to transform themselves and their social and physical environment for the better. Because the potential for new knowledge is limitless––so long as we protect and enable the institutions of science––we never have a basis for regarding any problem as insoluble. We endorse this confidence in the values of the Enlightenment, and applaud Deutsch’s rousing denunciations of timid and repressive anti-scientific con-servatism. Philosophical analysis cannot be expected to furnish a significant resolution to this battle between fundamentally conflicting attitudes. How-ever, scholarship in a much more general sense is highly relevant to thefight, since both scientism and conservatism are in thefinal analysis interpretations of history. Furthermore, as argued in the opening and closing pages of Ladyman and Ross (2007), the best motivation for trying to synthesize our scientific knowledge into a unified picture––that is, for building naturalistic metaphysics––is the crucial service this activity potentially performs in extending the Enlightenment project. If science is not seen to provide the basis for a general worldview, then people will continue to collectively confabulate alternative general pictures. This in turn matters because the confabulated pictures inspire groundless and usually wasteful and destructive politics and policy. We see no reason to be coy about the fact that, like the logical positivists, our philosophizing is inspired by a normative commitment:

while acknowledging the importance of conserving what is valuable, we abhor conservatism, which we view as a sad refusal to explore the magni fi-cent range of possibilities that our ability to do mathematics allows us, and thus betrays the best reason for caring passionately about objective truth.

The best general philosophy of science reveals a difficult tension between the ideas of objectivity, on the one hand, and readiness to let

theflow of new knowledge smash through conservative conceptual bar-riers, on the other hand. The tension in question is nicely demonstrated in Michael Friedman’s efforts to extend Kant’s philosophy of science in a strongly naturalist way, a project Friedman has shown through his histor-ical scholarship (Friedman, 1999) to have been the basic objective of our shared logical positivist heroes. The ambition is to safeguard the objectivity of scientific theory choice without downplaying the significance of the kind of radical theory change that has repeatedly swept through science, and especially through physics, since Kant sought to ground the objectiv-ity of Newtonian mechanics in synthetic a priori knowledge of necessary truths. Friedman (2001) rehabilitates the positivist project of separating the constitutive role of the a priori in establishing the framework within which empirical testing is possible from the idea that the content of the a priori is necessary and not revisable. For example, as discussed by Friedman in this volume, the concept of an inertial frame exemplifies the general fact that theories cannot be tested without background assumptions that implicitly define certain concepts needed to connect theoretical structure (in this case the notions of force and mass) with empirical data (such as the paths of the planets across the sky). Newton’s first law only holds in inertial frames in which, as a conceptual requirement, force-free bodies travel along straight lines. However, one can only establish that a body is force-free via Newton’s second law, which also only holds in inertial frames. The circularity here, while not vicious, has the consequence that the definition of an inertial frame cannot be tested directly but is rather required to get the business of testing Newton’s laws off the ground. Yet this status did not prevent Einstein from fundamentally altering the idea of an inertial frame in General Relativity. Thus, Friedman concludes, constitutive a priori principles can be revised and are not necessary; but while we have them they provide objective structure to scientific inquiry that avoids Quinean holism about confirmation and the attendant problem that theory choice seems to become a matter of taste (Quine, 1969).

Objectivity grounded in concept specification may not appear to be the real thing to many scientific realists––and certainly not to Deutsch. How-ever, let us put this purely philosophical issue to one side for now. Our concern here is that Friedman’s picture enjoins the same kind of cognitive inertia that Kuhn (1962) attributes to normal science. If Friedman’s account is correct, then unless a scientist is ready to replace the whole constitutive framework she must accept the a priori content of existing

science, and, since there are lots of incentives against doing the former, cognitive conservatism follows. Of course there is much cognitive conser-vatism in science, enforced by its peer review institutions. But to elevate conservatism to be part of a deep logic of science welcomes what Kuhn called‘the essential tension’ between science as juggernaut and science as custodian of accepted wisdom. Friedman’s work reconciles the positivists with Kuhn. But the picture of science as, at any given time, either in hyper-cautious normal mode or in ferment and riot mode––Kuhn’s revolutionary episodes––where rationality gives way to idiosyncrasies of taste is hardly comforting for those who hope that science might enable us to get a steadily clearer grip on the structure of general objective reality. Even those who consider Friedman’s account to be accurate with respect to normal science should recognize that it lacks resources for understanding the preservation of objectivity through episodes of profound theory change.

The leading critic of the positivists in their heyday was of course Popper. There has been a tendency for philosophers of science to regard Popper as something of an embarrassment. However, naturalistic philoso-phers should take it as an interesting fact about science that Popper has long been the favourite philosopher of science among scientists; and it would be condescending to attribute this entirely to the fact that Popper’s philosophy is relatively non-complex, self-contained, and flattering to scientists.4 A necessary condition for Popper’s appreciation by scientists is that he emphasizes themes they agree to be central: the provisional and dynamic nature of their knowledge, recognition of the creativity and indeed artistry involved in hypothesis formation, and acknowledgement that commitment to the institutional norms of scientific practice is an ethical stance with sweeping social and political implications. None of these themes are unique to Popper; but in his work they are fused into a philosophy that may not provide scientists with what philosophers wish scientists would want from them, namely metaphysical truth, but instead provide scientists with something else they value: affirming inspiration.

Deutsch is an avowed and uncritical follower of Popper, as one might

4 We have in mind here the fact that Popper often writes as if individual scientists, showing moral selflessness unique among modern institutional roles, heroically strive to refute their own theories. It is often pointed out that this describes the actual activity of very few scientists.

However, it is easy to strip this silliness out of Popper’s picture by noting that the greatest rewards in science are bestowed on those who make major revisions in the theories of others.

expect, seeing himself as reaffirming and extending the latter’s neo-Enlightenment manifesto.

We fully share this normative-institutional commitment. In welcoming much of what Deutsch has to say about science, we will thus implicitly be celebrating Popper too. We will ultimately concur with the majority of philosophers that metaphysical inspiration is not to be found in that source, and we will criticize Popper’s and Deutsch’s dismissal of the positivists.

Our aim is to show that when Deutsch’s errant metaphysical opinions are corrected, the result is a picture of science in which ontological and progressive enlightenment are mutually complementary.

One of Deutsch’s leading themes is not taken from Popper. This is his repeated claim that the most important epistemic function served by a scientific theory is not prediction or formal generalization, but explan-ation. Unfortunately he is not very explicit about what he understands explanations to be. He says only that they are‘assertions about what is out there and how it behaves’ (Deutsch, 2011: 3). This will strike philosophers as comically imprecise. However, Deutsch’s subsequent extensive discus-sions of examples makes clear that he means by explanation what most philosophers of science do: the embedding of claims about facts within networks of causal and nomological generalizations. Such explanations, he argues, here following Popper, are creative conjectures that resist easy adjustment in the face of recalcitrant tests. The epistemological ideal of falsifiable explanations that survive efforts at actual falsification is supple-mented by a complementary principle of maximum explanatory‘reach’.

This is a Lakatosian virtue: it is the capacity of explanatory strategies––

which Deutsch roughly identifies with the scientific theories that form the cores of Lakatosian research programmes––‘to solve problems beyond those that they were created to solve’. ‘Reach’, then, is what philosophers of science refer to as the capacity of theories to produce novel predictive success, and to support consilience and unification.

Deutsch emphasizes, just as Ladyman and Ross (2007) do, the remark-able fact that theories designed to explain phenomena observed locally and at parochial length and time scales familiar to humans have so often proved applicable to remote regions, and at more general scales than any human can directly experience. So, for example, we have never been anywhere near stars or their cores yet our theories explain their behaviour and the phenomena that they cause closer to home (p. 3). Deutsch emphasizes, however, that reliance on examples of this kind can mislead us into

thinking that how things seem to us pre-scientifically, on the basis of our limited engagement with our local environment and interests, should automatically generalize to less anthropocentric scales. He defends a principle of anti-parochialism, according to which we should self-consciously guard against mistaking appearance for reality and confusing local regularities with universal laws (p. 76). Furthermore, he argues that science and philosophy should take care to avoid a more specific sense of anthropocentrism, the projection of features of our experience and cogni-tion on to the non-human world. On the other hand, he argues that the

‘Principle of Mediocrity’ (p. 76), according to which humans are not cosmically special or significant, is also false, on the grounds that in certain respects, namely our capacity to generate knowledge and understand abstractions, and to radically redesign our own environments, humans are as far as we know unique among physical entities. Ladyman and Ross (2007: 2) stress our ability to do mathematics as a necessary condition for this. Deutsch often writes as if that ability is also a sufficient condition for the limitless proliferation of explanations with reach, so long as scien-tific institutions are not politically repressed. We think this idea is plausible, and we hope the future bears it out.

Deutsch grounds these principles in an account of observation and the evidential basis of science. He argues against‘empiricism’, defined as the view that all knowledge is inductively derived from sensory experience.

Again following Popper, Deutsch asserts that explanations cannot be based on induction because they transcend the features of the observations they explain––and not merely logically, in the sense of universally quantifying over them, but qualitatively. A second aspect of Deutsch’s anti-empiricism is his insistence that scientific observation is inherently theory laden, in the sense that all data are gathered, transduced, and systematized by means of instruments built to purposes informed by theory. Deutsch does not take this to impugn the status of observation, after the fashion among strong social constructivists, but rather to enrich the range of what ought to count as instances of observation. So, for example, an expert eye studying a photographic plate exposed by a telescope sees stars. Among candidates for the status of‘genuinely observed’ in the processing chain leading back from worldly objects, to images on the retina, to electrical signals in the optic nerve and so on, the project of selecting a stable‘winner’ by means of philosophical analysis is misguided in principle. Thus we should conclude that if our theory tells us that what produced a visual image used to

represent the data from a radio telescope is a galaxy then we are entitled to say that an astronomer looking at the image sees the galaxy.

According to Deutsch, empiricism historically replaced a conception of knowledge based on human authority with one based on the equally false authority of sense experience and induction. Endorsing the view that there is no ‘reliable means of justifying ideas as being true or probable’, he favourably contrasts this‘fallibilism’ with ‘justificationism’.

Here wefind Deutsch embracing an egregiously uncharitable Popper-ian criticism of the positivists, mixed with sound insight into the theme identified at the opening of the present section that goes to the core of the relationships between naturalism and Enlightenment values. The confu-sion is that Deutsch clearly imagines––perhaps misled by the surface semantics of the word‘confirmation’––that the aim of gathering evidence for scientific generalizations is certainty. Deutsch rightly castigates such an aim as contrary to the scientific attitude; however its attribution is utterly unfair to his leading examplars of‘bad philosophy’, the logical positivists and empiricists. Early in his book he denounces justificationism for embracing the project of‘securing ideas against change’ (p. 9). As discussed earlier, however, the positivists’ fundamental project was to reconcile Kant’s project of grounding the objectivity of specific observations in prior categorical and intellectual structure with the recognition, forced by Einstein’s physical vindication of non-Euclidean geometry, that appar-ently a priori grounds are revisable in light of experience. As explained by Friedman (1999), the positivists resorted to conventionalism as a way of achieving this reconciliation. This offers something weaker than what Deutsch’s ultimately ontological quest for objectivity demands. However, since conventions are obviously provisional by nature on anyone’s account, it is clearly rash to accuse the positivists of hoping to block conceptual or theoretical change. On the other hand, in supposing that our confidence in science might be buttressed by appeal to extra-scientific elements of thought and belief––specifically, in the case of the positivists, to formal logic––the positivists indeed accepted the anti-naturalist view of scientific beliefs as standing to benefit from extra-scientific securitization.

For Carnap, Neurath, or Reichenbach the securitization in question was not so much against change as against instantaneous doubt. However, early analytic philosophy indeed thereby opened the door, in its founding documents, to what has since metastasized, in contemporary analytic metaphysics, into a whole-scale elaboration of scientifically untutored

and logically elaborated intuitions, often for purposes of defence against challenges to conceptual comfort from science (Ladyman and Ross, 2007, Chapter 1).

We do not here mean to imply that if we could bring the positivists into the twenty-first century they would be sympathetic to analytic metaphys-ics. Friedman has shown us exactly what they could think instead––how, indeed, they could comfortably maintain their naturalism.5 Our point, instead, following Wilson (2006, and this volume) is that in assigning a foundational role to logic as a source of ‘clarification’ in specifying the meaning of scientific propositions––and thereby ‘clarifying’ scientists’

ontological commitments––the positivists in all innocence prepared the boggy ground in which so much philosophy flounders today, where instrumental control of the world of experience is granted as the domain of science and‘deep’ ontology is assigned as a task for a priori analysis.

Deutsch has no patience with instrumentalism, defined as the view that science merely summarizes observations while avoiding association of theor-etical structures with commitment to an underlying reality that corresponds to them (p. 31). He instead advocates realism, defined as the view that we can and do have knowledge of the actual structure of the physical world. He argues that science is progressive in the sense that the truth of old theories lives on in their successors (p. 113), maintains that this applies not only to predic-tions but also to explanapredic-tions, and so asserts that events like the replacement of Newtonian mechanics by quantum mechanics is no threat to realism.

Ladyman and Ross (2007) also defend all of these theses, based entirely on premises about the history and practice of theory construction and adjust-ment in the history of physics. Finally, Deutsch’s realism incorporates denial of the empiricist idea that scientific theories can generally be separated into formal cores and empirical interpretations. This is an interesting and contro-versial thesis that can only profitably be argued on the basis of carefully considered examples from science. It has received a sustained and highly persuasive such defence in Wilson (2006) (see also Wilson’s second chapter, Chapter 9, in this volume). We will return to the issue in some detail below.

The claims reviewed to this point are the basis for Deutsch’s positive philosophy of science, including its naturalized metaphysics. This consists

5 Historians of philosophy argue over the extent to which the actual Carnap anticipated or indeed fathered a different version of naturalism, namely Quine’s––which, as Friedman complains, in many moods suggests giving up on objectivity.

of two fundamental components. Thefirst is a repudiation of reduction-ism, and a commitment to the reality of causally efficacious emergent phenomena. The second is the claim that abstract entities can be real and can have real causal powers, notwithstanding that causation is itself held to be an abstraction (p. 124). Deutsch argues for thefirst claim just as Lady-man and Ross (2007, Chapter 4) do, by invoking the fact that in scientific practice, explanations of macro-scale phenomena in microphysical terms are almost never available. Rather, micro-scale complexity resolves itself into macro-scale simplicity (pp. 108–9), and so we explain macro-scale phenomena in macro-scale terms. Macro-scale entities, properties, and processes are emergent but since theyfigure in explanations and indeed causal explanations they are nonetheless real. By the same token, since sometimes the best explanation of a phenomenon cites an abstract entity or property, we ought also to believe in the reality of such abstractions. For example, the best explanation of a physical event such as the removal of a chess piece from a board may be that a computer programme is better than its human opponent at chess (pp. 114–15). As Ladyman and Ross (2007), along with Batterman (2002) argue at length, this is the only picture that

of two fundamental components. Thefirst is a repudiation of reduction-ism, and a commitment to the reality of causally efficacious emergent phenomena. The second is the claim that abstract entities can be real and can have real causal powers, notwithstanding that causation is itself held to be an abstraction (p. 124). Deutsch argues for thefirst claim just as Lady-man and Ross (2007, Chapter 4) do, by invoking the fact that in scientific practice, explanations of macro-scale phenomena in microphysical terms are almost never available. Rather, micro-scale complexity resolves itself into macro-scale simplicity (pp. 108–9), and so we explain macro-scale phenomena in macro-scale terms. Macro-scale entities, properties, and processes are emergent but since theyfigure in explanations and indeed causal explanations they are nonetheless real. By the same token, since sometimes the best explanation of a phenomenon cites an abstract entity or property, we ought also to believe in the reality of such abstractions. For example, the best explanation of a physical event such as the removal of a chess piece from a board may be that a computer programme is better than its human opponent at chess (pp. 114–15). As Ladyman and Ross (2007), along with Batterman (2002) argue at length, this is the only picture that