Most of us believe that theory-change in science has been a rationally analysable process. We believe, that is, that when one theory, Newton’s for example, is replaced as the accepted theory in science by a rival, Einstein’s in the same example, it is because the newer theory turns out to be better than the old in some objective sense and a sense, moreover, crucially related to the experimental evidence. Even those who have abjectly surrendered (at any rate on Mondays, Wednesdays (...) and Fridays) to an overly subjectivist form of Bayesianism, believe this really – hence their desperate pointing in the direction of (in my view, unavailing) results concerning the ‘washing out of priors’. The problem has always been to construct a set of agreed criteria of theory-appraisal that would convincingly yield this generally agreed result. (Of course by ‘most of us’ here I mean ‘most philosophers of science’; nothing I say will cut much ice with some of our benighted sociologist colleagues.). (shrink)
JOHN WORRALL (ABOUT TO APPEAR –W ITH REPLY BY DEL RATZCH – IN PETERSON AND VANARRAGON (EDS) CONTEMPORARY DEBATES IN THE PHILOSOPHY OF RELIGION. BLACKWELL) We get the ages of rock, and they get the rock of ages; we work out how the heavens go and they work out how to get to heaven.
The appeal of scientific realism is chiefly based on the – staggering – empirical success of the theories currently accepted in science. The realist exhibits some currently accepted scientific theory (the General Theory of Relativity, say), points to its astounding empirical success (with the gravitational redshift, the precession of Mercury’s perihelion, etc) and suggests that it would be monumentally implausible to suppose that the theory could score such empirical successes and yet not reflect, at least to some good approximation, the (...) underlying nature of reality. To hold that combination of beliefs would be, in Poincaré’s celebrated phrase (1905/1952, p. 150), “to attribute an inadmissible role to chance”. (shrink)
Worrall ([1989]) argued that structural realism provides a ‘synthesis’ of the main pro-realist argument – the ‘No Miracles Argument’, and the main anti-realist argument – the ‘Pessimistic Induction’. More recently, however, it has been claimed (Howson [2000] and Lewis [2001], respectively) that each of these arguments is an instance of the same probabilistic fallacy – sometimes called the ‘base-rate fallacy’. If correct, this clearly seems to undermine structural realism and Magnus and Callender have indeed claimed that both arguments are fallacious (...) and ‘without [them] we lose the rationale for … structural realism’ ([2004], p. 333). I here argue that what have been shown to be fallacious are simply misguided formalisations of ‘the’ arguments and that when they are properly (and modestly) construed they continue to provide powerful motivation for favouring structural realism. (shrink)
Are theories ‘underdetermined by the evidence’ in any way that should worry the scientific realist? I argue that no convincing reason has been given for thinking so. A crucial distinction is drawn between data equivalence and empirical equivalence. Duhem showed that it is always possible to produce a data equivalent rival to any accepted scientific theory. But there is no reason to regard such a rival as equally well empirically supported and hence no threat to realism. Two theories are empirically (...) equivalent if they share all consequences expressed in purely observational vocabulary. This is a much stronger requirement than has hitherto been recognised—two such ‘rival’ theories must in fact agree on many claims that are clearly theoretical in nature. Given this, it is unclear how much of an impact on realism a demonstration that there is always an empirically equivalent ‘rival’ to any accepted theory would have—even if such a demonstration could be produced. Certainly in the case of the version of realism that I defend—structural realism—such a demonstration would have precisely no impact: two empirically equivalent theories are, according to structural realism, cognitively indistinguishable. (shrink)
Obviously medicine should be evidence-based. The issues lie in the details: what exactly counts as evidence? Do certain kinds of evidence carry more weight than others? (And if so why?) And how exactly should medicine be based on evidence? When it comes to these details, the evidence-based medicine (EBM) movement has got itself into a mess – or so it will be argued. In order to start to resolve this (...) mess, we need to go 'back to basics'; and that means turning to the philosophy of science. The theory of evidence, or rather the logic of the interrelations between theory and evidence, has always been central to the philosophy of science – sometimes under the alias of the 'theory of confirmation'. When taken together with a little philosophical commonsense, this logic can help us move towards a position on evidence in medicine that is more sophisticated and defensible than anything that EBM has been able so far to supply. (shrink)
John Worrall (2010). Error, Tests, and Theory Confirmation. In Deborah G. Mayo & Aris Spanos (eds.), Error and Inference: Recent Exchanges on Experimental Reasoning, Reliability, and the Objectivity and Rationality of Science. Cambridge University Press.
In a randomized clinical trial (RCT), a group of patients, initially assembled through a mixture of deliberation (involving explicit inclusion and exclusion criteria) and serendipity (which patients happen to walk into which doctor’s clinic while the trial is in progress), are divided by some random process into an experimental group (members of which will receive the therapy under test) and a control group (members of which will receive some other treatment – perhaps placebo, perhaps the currently standard treatment for the (...) condition at issue). In a ‘double blind’ trial neither the patient nor the clinician knows to which of the groups a particular patient belongs. The results of double blind randomized controlled trials are almost universally regarded as providing the ‘gold standard’ for evidence in medicine. Fairly extreme claims to this effect can be found in the literature. For example the statistician Tukey wrote (1977, p. 679) “almost the only source of reliable evidence [in medicine] … is that obtained from … carefully conducted randomised trials”. And the clinician Victor Herbert claimed (1977, p. 690) “..the only source of reliable evidence rising to the level of proof about the usefulness of any new therapy is that obtained from wellplanned and carefully conducted randomized, and, where possible, coded (double blind) clinical trials. [Other] studies may point in a direction, but cannot be evidence as lawyers use the term evidence to mean something probative … [that is] tending to prove or actually proving”. Finally, the still very influential movement in favour of ‘Evidence Based Medicine’ (EBM) that began at McMaster University in the 1980s was initially often regarded as endorsing the claim that only RCTs provide real scientifically telling evidence. (shrink)
The evidence from randomized controlled trials (RCTs) is widely regarded as supplying the 'gold standard' in medicine-we may sometimes have to settle for other forms of evidence, but this is always epistemically second-best. But how well justified is the epistemic claim about the superiority of RCTs? This paper adds to my earlier (predominantly negative) analyses of the claims produced in favour of the idea that randomization plays a uniquely privileged epistemic role, by closely inspecting three related arguments from leading contributors (...) to the burgeoning field of probabilistic causality-Papineau, Cartwright and Pearl. It concludes that none of these further arguments supplies any practical reason for thinking of randomization as having unique epistemic power. (shrink)
Who are the major figures that have shaped philosophy of science in Britain? What impact has the subject had in Britain outside academic philosophy? How have two of the major centers of the subject - in Pittsburgh and in London - interacted over the years? I begin by looking briefly at the recent history of philosophy of science in Britain and its general impact (tying this in with its interaction with the Pittsburgh Center and Pittsburgh people. It seems to me, (...) though, that the best way to celebrate an anniversary like that of the Pittsburgh Center is by predominantly looking forward rather than back. And I concentrate in this lecture on showing how philosophy of science can have an impact on issues of current concern, in Britain and more generally. (shrink)
[Peter Lipton] From a reliabilist point of view, our inferential practices make us into instruments for determining the truth value of hypotheses where, like all instruments, reliability is a central virtue. I apply this perspective to second-order inductions, the inductive assessments of inductive practices. Such assessments are extremely common, for example whenever we test the reliability of our instruments or our informants. Nevertheless, the inductive assessment of induction has had a bad name ever since David Hume maintained that any attempt (...) to justify induction by means of an inductive argument must beg the question. I will consider how the inductive justification of induction fares from the reliabilist point of view. I will also consider two other well-known arguments that can be construed as inductive assessments of induction. One is the miracle argument, according to which the truth of scientific theories should be inferred as the best explanation of their predictive success; the other is the disaster argument, according to which we should infer that all present and future theories are false on the grounds that all past theories have been found to be false. \\\ [John Worrall] Science seems in some ways to have been remarkably successful. What does this success tell us about the epistemological status of current scientific claims? Peter Lipton considers various meta-inductive arguments each of which start from premises about science's 'track record'. I show that his endorsements of the 'strongest' of these are, on analysis, remarkably weak. I argue that this is a reflection of difficulties within the general epistemological framework that he adopts-that of reliabilism. Finally, I briefly outline the quite different approach that I take to this issue, in the process responding to Lipton's criticisms of the 'pessimistic meta-induction'. (shrink)
[Peter Lipton] From a reliabilist point of view, our inferential practices make us into instruments for determining the truth value of hypotheses where, like all instruments, reliability is a central virtue. I apply this perspective to second-order inductions, the inductive assessments of inductive practices. Such assessments are extremely common, for example whenever we test the reliability of our instruments or our informants. Nevertheless, the inductive assessment of induction has had a bad name ever since David Hume maintained that any attempt (...) to justify induction by means of an inductive argument must beg the question. I will consider how the inductive justification of induction fares from the reliabilist point of view. I will also consider two other well-known arguments that can be construed as inductive assessments of induction. One is the miracle argument, according to which the truth of scientific theories should be inferred as the best explanation of their predictive success; the other is the disaster argument, according to which we should infer that all present and future theories are false on the grounds that all past theories have been found to be false. \\\ [John Worrall] Science seems in some ways to have been remarkably successful. What does this success tell us about the epistemological status of current scientific claims? Peter Lipton considers various meta-inductive arguments each of which start from premises about science's 'track record'. I show that his endorsements of the 'strongest' of these are, on analysis, remarkably weak. I argue that this is a reflection of difficulties within the general epistemological framework that he adopts-that of reliabilism. Finally, I briefly outline the quite different approach that I take to this issue, in the process responding to Lipton's criticisms of the 'pessimistic meta-induction'. (shrink)
Fresnel's theory of light was (a) impressively predictively successful yet (b) was based on an "entity" (the elastic-solid ether) that we now "know" does not exist. Does this case "confute" scientific realism as Laudan suggested? Previous attempts (by Hardin and Rosenberg and by Kitcher) to defuse the episode's anti-realist impact. The strongest form of realism compatible with this case of theory-rejection is in fact structural realism. This view was developed by Poincare who also provided reasons to think that it is (...) the only realist view of theories that really makes sense. (shrink)
Abstract This paper attempts to clarify the debate between those philosophers who hold that the development of science is governed by objective standards of rationality and those sociologists of science who deny this. In particular it focuses on the debate over the ?symmetry thesis?. Bloor and Barnes argue that a properly scientific approach to science itself demands that an investigator should seek the same general type of explanation for all decisions and actions by past scientists, quite independently of whether or (...) not she or he happens to agree with those decisions or approve those actions as ?correct? or ?rational?. I try to improve on previous treatments of the ?rationalist? position (by Lakatos, Laudan, Newton?Smith and Brown) and clarify the exact asymmetries to which the ?rationalist? is, and is not, committed. (shrink)
The no-miracles argument for realism and the pessimistic meta-induction for anti-realism pull in opposite directions. Structural Realism---the position that the mathematical structure of mature science reflects reality---relieves this tension.
