Philosophy of Science: Post-positivism, part II

Transcription

1 Philosophy of Science: Post-positivism, part II Kristina Rolin 2012 Positivism (logical empiricism) Empiricism: Scientific knowledge is based on observation statements (which are understood to be basic beliefs). Logical: Philosophy of science aims to reconstruct the logical structure of scientific knowledge (e.g., rules that can be used to connect observation statements to hypotheses and theories). Unity of the sciences: All sciences are united by certain epistemic goals and methods. 1

2 Verificationism Synthetic Theory Analytic Translation Translation Synthetic Observation statements Observation statements Observation statements Quine s holistic empiricism Only a web of beliefs can have empirical content, not a single belief. Therefore, we cannot test a single hypothesis in isolation (the Duhem-Quine thesis). Observation Theory Assumption Pierre Duhem ( ) Assumption Observation 2

3 Quine s Epistemology naturalized Analytic A priori A posteriori The meaning of words rests ultimately on experience. Synthetic Empirical truths are the proper object of science and philosophy. 3

4 Thomas Kuhn ( ) The Structure of Scientific Revolutions (1962): The image of science has been drawn mainly from the study of finished scientific achievements as these are recorded in the classics and textbooks. The aim is to sketch a different concept of science that can emerge from the historical record of the research activity itself (1). Two kinds of naturalism Quine: Epistemology, or something like it, simply falls into place as a chapter of psychology and hence of natural science. Kuhn: How could history of science fail to be a source of phenomena to which theories about knowledge may legitimately be asked to apply? (Kuhn 1962, 9) 4

5 Kuhn s holism in epistemic justification The epistemic justification of hypotheses and theories takes place within a paradigm which is characterized by (1) particular beliefs (prevailing scientific theories, beliefs about proper methods, standards of argumentation, and epistemic values), and (2) examples of scientific problems and their solutions. Kuhn s notion of paradigm Kuhn in the 1969 Postscript to The structure of scientific revolutions: On the one hand, it stands for the entire constellation of beliefs, values, techniques, and so on shared by the members of a given community. On the other, it denotes one sort of element in that constellation, the concrete puzzle-solutions which, employed as models of examples, can replace explicit rules. ([1962] 1996, 175). Towards the end of his career Kuhn settled on the latter meaning of the term, the notion of paradigm as a concrete exemplar. Kuhn s notion of paradigm as an exemplar anticipates contemporary research on the role of models in science (Wray 2011, 63-64). 5

6 Kuhn s underdetermination thesis The early developmental stages of most sciences have been characterized by continual competition between a number of distinct views of nature, each partially derived from, and all roughly compatible with, the dictates of scientific observation and method (4). Observation and experience can and must drastically restrict the range of admissible scientific belief, else there would be no science. But they cannot alone determine a particular body of such belief (4). More on paradigms Successive paradigms tell us different things about the population of the universe and about that population s behavior. (103) But paradigms differ in more than substance, for they are directed not only to nature but also back upon the science that produce them. They are the source of the methods, problem-field, and standards of solution accepted by any mature scientific community at any given time. (103) The reception of a new paradigm often necessitates a redefinition of the corresponding science. Some old problems may be relegated to another science or declared entirely unscientific. (103) 6

7 More on paradigms Paradigms provide scientists not only with a map but also some of the directions essential for map-making. (109) When paradigms change, there are usually significant shifts in the criteria determining the legitimacy both of problems and of proposed solutions. (109) Each paradigm will be shown to satisfy more or less the criteria that it dictates for itself and to fall short of a few of those dictated by its opponent. ( ) Theory-ladenness of observation Observation reports do not provide a foundation for scientific knowledge. Scientific fact and theory are not categorically separable, except perhaps within a single tradition of normal-scientific practice (Kuhn 1962, 7). 7

8 Normal science Scientific inquiry is tradition-bound (and scientists are not as critical and open-minded as Popper assumed them to be). The so called normal science takes place within a paradigm ( puzzlesolving ). Normal research, which is cumulative, owes its success to the ability of scientists regularly to select problems that can be solved with conceptual and instrumental techniques close to those already in existence. (96) Without commitment to a paradigm there could be no normal science. (100) Anomalies In science, as in the playing card experiment, novelty emerges only with difficulty, manifested by resistance, against a background provided by expectation. (Kuhn 1962, 64) Anomaly appears only by the background provided by the paradigm. (Kuhn 1962, 65) Bruner & Postman On the perception of incongruity: a paradigm. 8

9 Scientific revolutions The development of scientific knowledge is not always cumulative. Scientific revolutions are the tradition-shattering complements to the traditionbound activity of normal science (6). Scientific revolutions are non-cumulative developmental episodes in which an older paradigm is replaced in whole or in part by an incompatible new one (92). Communication across the revolutionary divide is inevitably partial (149). Scientific revolutions Just because it is a transition between incommensurables, the transition between competing paradigms cannot be made a step at a time, forced by logic and neutral experience. Like the gestalt switch, it must occur all at once or not at all. (Kuhn 1962, 150) The transfer of allegiance from paradigm to paradigm is a conversion experience that cannot be forced. (151) 9

10 Scientific versus political revolutions Like the choice between competing political institutions, that between competing paradigms proves to be a choice between incompatible modes of community life. (94) As in political revolutions, so in paradigm choice there is no standard higher than the assent of the relevant community. (94) Scientific revolution is a displacement of the conceptual network through which scientists view the world (102). Incommensurability paradigm choice can never be unequivocally settled by logic and experiment alone. (94). The normal-scientific tradition that emerges from a scientific revolution is not only incompatible but often actually incommensurable with that which has gone before. (103) The proponents of competing paradigms will often disagree about the list of problems that any candidate for paradigm must resolve. Their standards or their definitions of science are not the same. (148) 10

11 Incommensurability Topic-incommensurability: There is no common measure by which to evaluate two or more theories. The lack of common measure is caused by different theories addressing different, merely partially overlapping sets of topics or problems. Value-incommensurability: Scientists are lead to work with different theories because they disagree about the standards of theory evaluation. Meaning-incommensurability: Scientists use the same terms in different senses thereby impeding their communication. Dissociation: The proponents of competing paradigms practice their trades in different worlds. (Kuhn 1962, 150) Topic-incommensurability? Topic incommensurability is a rather modest form of incommensurability. It does not imply that it is in principle impossible to find a common measure. Therefore, it does not imply that the resolution of disputes is necessarily irrational or non-rational. The thesis explains why the resolution of disputes in science is often a protracted affair (Wray 2011, 69-70). 11

12 Value-incommensurability? Throughout the history of science, scientific practices have been guided by the following epistemic values: accuracy, consistency, broad scope, simplicity, and fruitfulness. Rational disagreement is possible because scientists may interpret epistemic values in different ways and put them into different orders of priority. Accuracy, internal and external consistency, breadth of scope, simplicity, and fruitfulness are not so precise as to forbid scientists from interpreting them in different ways. Kuhn, Thomas Objectivity, value judgment, and theory choice, in Essential tensions. Meaning-incommensurability? Can a paradigm have radically different concepts that cannot be translated into the concepts of another paradigm? No, because the very idea of a conceptual scheme that is radically different from another conceptual scheme is incoherent. What is the content that the different conceptual schemes are assumed to organize? How can we identify them as different conceptual schemes in the first place? Davidson, Donald On the very idea of a conceptual scheme, in Inquires into truth and interpretation. 12

13 Meaning-incommensurability? 'Incommensurability' is only a problem given certain philosophical presuppositions: those of the reductionist theory of meaning, which requires the unit of common measure between comprehensive theories to be a theory-neutral observation language. (Nersessian 1982, 206) The genuine remaining problem is that of the development of a new theory of meaning in science. (Nersessian 1982, 205) Nersessian, Nancy Why is incommensurability a problem? Acta Biotheoretica 31, Trading zones? In the social sciences, many disciplines include a variety of paradigms (this is normal science). There is no reason to believe that communication across paradigms is in principle impossible. It is possible and feasible given that scientists have an interest in it. 13

14 Kuhn s later work The notion of scientific revolution as a paradigm change is replaced with the notion of scientific revolution as a taxonomic or lexical change (Wray 2011, 26). Meaning-incommensurability is replaced with local incommensurability (73). Kuhn gave up the individualist notion of gestalt shift in favor of a social account of scientific change (27). Kuhn introduced a new topic into philosophy of science: the creation of new scientific specialties (5). Kuhn s evolutionary epistemology Science is not aptly described as moving towards a fixed goal such as truth (Wray 2011, 8). Instead, scientists are moved by research agendas set by their predecessors, and they work with instruments and theories developed by their predecessors. Evaluation of theories is comparative (9). The fragmentation that results from increasing specialization in science is not a temporary stage in the development of science. Rather, it is the means by which scientists achieve their epistemic goals. (202) 14

15 Kuhn s social epistemology The locus of scientific change is a research community, and not merely an individual scientist (Wray 2011, 6). Kuhn is an internalist in the sense that he believes that changes in theory are ultimately caused by a consideration of epistemic factors, not factors external to science (11). Yet, Kuhn believes that philosophers of science need to draw on work in the sociology of science (146). Kuhn s philosophy of science is a social epistemology because he seeks to understand how the social dimensions of science contribute to the success of science (171). Division of labor Subjective factors are not properly called external factors in science because they can play an epistemic role in theory choice. They are responsible for ensuring that there is an efficient division of labor in science and competing theories are developed (Wray 2011, 183). It is only when competing theories are developed that the epistemic merits and shortcomings of the theories emerge. And only when the epistemic merits and shortcomings of competing theories are revealed can a rational choice be made between competing theories. (Wray 2011, 10) 15

16 Normative implications Kuhn asks us to judge changes in theory from the perspective of the research community rather than the perspective of the individual scientists involved (Wray 2011, 181). Hence, we are not necessarily committed to judging either the early converts or the holdouts to a change of theory as irrational or overstepping the bounds of rationality (182). It is a mistake to see Kuhn s account of science as a threat to the rationality of science (201). Kuhn s alleged irrationalism The new paradigm brings a totally new rationality. There are no super-paradigmatic standards. The change is a bandwagon effect. Thus in Kuhn s view scientific revolution is irrational, a matter for mob psychology. (Lakatos 1970, 178) 16

17 What is philosophy of science? Philosophy of science is a study of the normative conception of scientific knowledge: What criteria should research and knowledge fulfill in order to count as scientific research and knowledge? Method: The goal is to find a reflective equilibrium between normative principles (e.g. the goal of scientific inquiry should be truth or empirical success) and actual practices in the sciences. Normative in philosophy of science A normative theory makes explicit value judgments (e.g., judgments about what things should be and what should be done): Rational reconstruction of scientific knowledge (logical empiricism) Naturalized philosophy of science Psychology (Quine) History of science (Kuhn) 17

18 Normativity in naturalized PoS Normative approaches in philosophy of science offer accounts of how people ought to think. Since ought implies can, normative approaches must take into account that human beings are highly fallible cognitive systems, products of a lengthy evolutionary process (Kitcher 1992, 58). Normative approaches should specify the goals of scientific inquiry (e.g., significant truth and empirical success) and use empirical methods to find out the best means to achieve these goals (under some circumstances). Justification/discovery revisited The context of justification includes the ways in which scientific hypotheses and theories are actually argued for. This is important when we aim to understand the structure of a research paper ( writing science ). The context of discovery includes the ways in which scientists actually arrive at certain hypotheses and theories. This is important when we aim to understand the structure of a research process ( doing science ). Philosophy of science is concerned with the doing of science and the writing of science. Yet, we can make a distinction between two perspectives: descriptive and normative/evaluative. 18

19 Today s message Kuhn introduced novel concepts to understand scientific knowledge: Paradigm Normal science Anomaly Scientific revolution Incommensurability 19