«Hanson and Kuhn on Observation Reports and Knowledge Claims»

<( Hanson and Kuhn on Observation Reports and Knowledge Claims >> *

By Paul TIBBETTS

Summary For traditional empiricism, all empirical knowledge claims ultimately rest on the

foundation of theory-neutral observation statements; the latter in turn are mapped into sensory experience of the external world. This version of the foundation metaphor has been attacked on at least three grounds: from psychological studies on human perception; from an analysis of the logic of observation concepts, especially “seeing”, “seeing as”, and “seeing that”; and from case studies from the history of science showing the supposed paradigm-dependent character of observation language. These three critiques of the foundation metaphor are summarized in statement (P): “There are no theory- neutral knowledge claims”. The evidence offered by Hanson and Kuhn in support of (P) is then analyzed in some detail, together with the question whether (P) is necessarily or only contingently true. It is suggested that only the weaker, contingently true version of (P) is defendable, in opposition to both Hanson and Kuhn. A distinction is then introduced between two types of observation reports: reports concerning seeing as discrimination and reports of seeing as interpreting. In defense of the foundation metaphor, it is argued that (P) is compatible with the claim that “There are theory- neutral observation statements”, given that at least some observation statements (those reporting figure-ground discriminations) are not knowledge claims. I t is suggested that in his later writings even Hanson distinguished between “pure-visual-experience seeing” and knowledge claims proper.

Resum6 Pour l’empirisme traditionnel, tous les postulats de connaissance empirique re-

posent en dernikre analyse sur la justification d’CnoncCs d’observation neutres par rapport B toute thCorie; ces CnoncCs sont h leur tour mis en relation avec l’expkrience sensible du monde extbrieur. Cette version de la mCtaphore du fondement a CtC attaquCe pour au moins trois raisons: partir d’6tudes psychologiques de la perception hu- maine, h partir de l’analyse logique des concepts dobservation, en particulier de u voir s, avoir tel,, uvoir que,, enfin B partir de 1’Ctude de cas tires de l’histoire des sciences en montrant la dCpendance du langage de l’observation v is -h is des paradigmes. Ces trois critiques de la mCtaphore du fondement sont rCsum6es par 1’6nonc6 (P): a I1 n’y a pas de postulats de connaissance indipendants de toute thCorie s. Les arguments de Kuhn et Hanson en faveur de (P) sont ensuite analysCs en dCtail, en m h e temps que

* This paper was awarded the 1975 Richard M. Griffith Memorial Award in Philosophy at the annual meeting of the Southern Society for Philosophy and Psycho- logy, held New Orleans, March 27-29, 1975. I wish to thank my colleague Professor Raymond Herbenick for his critical comments at numberous points in this paper.

Dialectica Vol. 29, No 2-3 (1975)

146 Paul Tibbetts

la question si (P) est une vtritt ntcessaire ou contingente. L‘auteur suggkre, en opposition avec Kuhn et Hanson, que seule la version faible de (P) (contingente) peut &tre soutenue. I1 introduit ensuite une distinction entre deux types de rapports d’observation: rapports sur une a vision en tant que discrimination B et rapport sur une a vision en tant qu’interprttation s. I1 montre, pour la dtfense de la mitaphore du fondement, que (P) est compatible avec le postulat: a I1 existe des CnoncCs d’observation neutres par rapport ?J toute thtorie s, pour autant qu’il y ait au moins quelques BnoncCs d’observation (ceux concernant des discriminations basCes sur des formes) ne sont pas des postulats de connaissance. M&me Hanson dans ses derniers Ccrits distingue entre a la perception empirique purement visuelle B et les postulats de connaissance propre- ment dits.

Zusammenfassung Dem traditionellen Empirismus gemass beruht unsere Erkenntnis letztlich auf

theorieneutralen Beobachtungsaussagen; diese ihrerseits bilden die sinnlichen Erfah- rungen, die wir von der Aussenwelt haben, ab. Diese Auffassung wurde in dreifacher Hinsicht angefochten: auf Grund der Ergebnisse von psychologischen Studien iiber menschliche Wahrnehmungsprozesse; auf Grund logischer Analyse von Beobach- tungstermen (im besonderen der Ausdriicke asehens, sehen ah,, und asehen, d a m ) ; und auf Grund von Fallstudien aus der Geschichte der Wissenschaft, die den par- digmaabhangigen Charakter der Beobachtungssprache nachweisen sollen. Diese drei Aufsatze einer Kntik an der Begrundungsstrategie der logischen Empiristen lassen sich in folgendem Satz (P) zusammenfassen: aEs gibt keine theorieneutralen Wissens- anspriiche., Diese Belege, die Hanson und Kuhn zugunsten von (P) anfiihren, werden genauer untersucht - zugleich mit der Frage, ob (P) notwendig, cxler nur faktisch wahr ist. Es scheint, dass, entgegen der Ansicht von Hanson und Kuhn, sich vor allem die schwachere These - diejenige der kontingenten Wahrheit - vertreten lasst. Dann wird eine Unterscheidung zwischen zwei Arten von Beobachtungsweisen eingefiihrt: dehen als Diskrimination, und aSehen als Interpretations. Auf Grund dieser Unter- scheidung wird gezeigt, dass (P) vereinbar ist mit der Forderung nach theorieneutralen Beobachtungssatzen - vorausgesetzt, dass gewisse Beobachtungsaussagen (dieje- nigen namlich, die FiguriHintergrund-Unterscheidungen betreffen) keine Erkenntnis- anspriiche erheben. Es scheint, dass selbst Hanson in seinen spateren Schriften den Unterschied zwischen arein visuellem Sehen, und theoriegeladenem Sehen gemacht hat.

According to empiricism, all empirical knowledge claims can in principle be arranged in a hierarchy of increasing abstractness and universality, the lowest ‘ level ’ or foundation of which consists of theory-neutral observation statements. These observation statements, in turn, correspond to or are ‘ mapped into ’ sensory experience of an external world. As Russell wrote in Our Knowledge of the External World,

The first thing that appears when we begin to analyze our com- mon knowledge is that some of it is derivative, while some is primitive; that is to say, there is some that we believe because of something else from which it has been inferred in some sense, while other parts are believed on their own account, without the support of any outside evidence. It is obvious that the senses give knowledge of the latter kind: the immediate facts perceived by sight or touch or hearing do not need to be proved by argument, but are completely self-evident.

Hanson and Kuhn on Observation Reports and Knowledge Claims 147

What does not go beyond our own personal sensible acquaintance must be for us the most certain: the ‘ evidence of the senses ’ is pro- verbially the least open to question (1).

In his early ‘ empiricist period ’, James could also talk about sensations as the terminous a quo and the terminus ad quem of thought; conceptual systems were to be grounded in sensations as bridges plunge their piers into rock. Accordingly, “ conceptual systems which neither begin nor left off in sensations would be like bridges without piers ” (2).

The foundation metaphor, together with the thesis that theoretical terms and observation terms constitute separate semantic classes, has been seriously undermined by Hanson, Kuhn, Sellars, and others. Though qualifications and refinements will later be introduced, attacks on the empiricist thesis above have been expressed as follows. Hanson: “ theories and interpretations are ‘ there ’ in the seeing from the outset ” (3); “ seeing is a ‘ theory-laden ’ under- taking [and] observation of X is shaped by prior knowledge of X” (4); and “ interpretation, i. e., seeing as and seeing that, is built into the very concept of seeing ” (5). Kuhn: the appeal to a “ neutral language of observations now seems to me hopeless ” (6), and “No language restricted to reporting a world fully known in advance can produce neutral and objective reports on ‘the given ’. Philosophical investigation has not yet provided even a hint of what a language able to do that would be like ” (7).

For now, let us summarize the thrust of Hanson and Kuhn’s attacks as statement (P): There are no theory-neutral empirical knowledge claims. According to (P), and in opposition to empiricism, there are in principle no observation statements which are sufficient for adjudicating between compet- ing scientific hypotheses. This follows given that there are no logically sufficient criteria by means of which the meaning of observation terms can be established without reference to the theoretical vocabulary.

With this in mind, there are three issues regarding (P) which will be discussed in this paper. First, the question as to what types of evidence are offered by Hanson and Kuhn in justification of (P). Secondly, is this evidence sufficient to warrant the thesis that (P) is a necessary rather than a contingently true assertion? Thirdly, is (P) incompatible with the claim (a) that there are theory neutral observation statements? My motive for raising these issues derives from the variety of ways in which Hanson and Kuhn argue for (P). Sometimes (P) functions as an empirical generalization concerning the way ordinary people and scientists perceive their world(s), whereas at other times (P) seems to function as a synthetic a priori proposition. Consequently, it is far from clear whether Hanson and Kuhn (and other critics of empiricism

148 Paul Tibbetts

and the foundation metaphor) defend (P) on empirical grounds or as a ‘ constitutive principle’ in Kant’s sense. Though restricting myself to a specific issue in the writings of Hanson and Kuhn, I have the same sort of uneasiness regarding (P) as Feyerabend does with related themes.

Whenever I read Kuhn, I am troubled by the following question: are we here presented with methodological prescriptions which tell the scientist how to proceed; or are we given a description, void of any evaluative element, of those activities which are generally called ‘ scientific ’? Kuhn’s writings, it seems to me, do not lead to a straight- forward answer. They are ambiguous in the sense that they are compatible with, and lend support to, both interpretations (8).

When (P) is construed as simply an empirical generalization, derived from psychological studies on perception or from case studies in the history of science, we have the weak version of (P), hereafter referred to as (Pw). Consersely, when (P) is taken to be constitutive of all perceptual experience and therefore necessarily rather than contingently true of experience, we have the strong version of (P), or (Ps). Where (Pw) is supported by relevant empirical and historical evidence, such evidence is entirely irrelevant to establishing the truth of (Ps). Interestingly, Hanson and Kuhn both defend (Pw) in addition to (Ps), as though (Ps) is somehow reinforced by the evidence adduced for (Pw). This is in sharp contrast with Kant’s defense of (Ps); he seldom if ever strengthens his arguments (regarding the role of the categories and the forms of intuition in the synthesis of experience) by psychological or other empirical considerations. Kant clearly recognized, as did Wittgenstein in On Certainty, that a transcendental argument is quite different from an argument based on empirical evidence. Let us now turn to (Pw) and (Ps) in Hanson’s

Regarding (Pw), Hanson devotes considerable space to psychological studies, especially Gestalt psychology: the shifting (Schroder) staircase, the Necker cube, the old Parisienne-young girl figure, the antelope-bird figure, the vase-two faces drawing, and so on. In a footnote, after citing a number of psychological studies by Kiilpe, Boring, Wertheimer, and others, he adds that “ discussions of perception could not but be improved by the reading of these twenty papers ” (9), which seems somewhat strange given his recognition on the same page that “ philosophy has no concern with fact, only with conceptual matters ”. Concerning (Pw) and the history of science, Hanson refers to the controversy between Tycho Brahe and Kepler concerning whether the sun moves relative to the earth at sunrise or vice versa. This and other con- flicts in the history of science suggest to Hanson that the respective con-

writings.


ceptual organizations of the two scientists are vastly different, and that where “ Tycho and Simplicius see a mobile sun, Kepler and Galileo see a static sun ” (10). Hanson’s unending references to developments in Renaissance astronomy, to Aristotle, Galileo and Descartes on freely falling bodies and the concept of acceleration, to Einstein, De Broglie, and Bohm on the uncer- tainty principle, and to Galileo, Newton, and Hume on causal sequences, all serve to support (Pw).

However, Hanson extrapolates from (Pw) to (Ps) when he goes on to state that (P) is “ inextricable and indispensable ” to observation in physical science. It should be noted, though, that Hanson later recognized that (Ps)

is a stronger claim, requiring a stronger argument. Let us put it differently; that observation in physics is not an encounter with unfamil- iar and unconnected flashes, sounds and bumps, but rather a calcu- lated meeting with these flashes, sounds and bumps of a particular kind - this might figure in an account of what observation is. But1 it would not secure the point that observation could not be otherwise. This latter type of argument is now required: it must establish that an alternative account would be not merely false, but absurd (11).

The ‘ stronger claim ’ is especially evident in his later book, Perception and Discovery. Hanson there talks about interpretation, or seeing as and seeing that, as “ built into the very concept of seeing’’ (12). In further defense of (Ps), he goes on to talk about knowledge, experience, and language as “ spectacles that we wear behind our eyes ”. However, rather than generalizing from (Pw) to (Ps), Hanson now argues that (Ps) follows given an analysis of the logic of observation concepts (13). Accordingly, at this point Hanson shifts from an empirical account of perception and observation reports into a linguistic analysis of the concepts “ seeing as ” and “ seeing that ”. For example, one sees a diagram or a visual object as a three-dimen- sional figure, and one sees that ice will melt at a certain temperature. “ See that ” and “ seeing that ” expressions are always followed by sentential clauses. Consequently, for syntactical rather than for extra-linguistic or empirical reasons, one can not see that ice-cubes, but only that ice-cubes melt. “ Tycho and Simplicius see that the universe is geocentric; Kepler and Galileo see that it is heliocentric ”. This linguistic stipulation shows that the structure of seeing that clauses is not dictated by empirical but by syntactical considerations. Supposedly, Hanson feels that his discussion of this point enlists support for (Ps). This amounts to the claim that that is followed by a complete sentential unit in the English language. Given that perceptual orga- nization is shaped by sentence structure and linguistic considerations for Hanson, (Ps) is consequently a justifiable hypothesis.

150 Paul Tibbetts

As suggested above, it is because Hanson is concerned with establishing (Ps) in addition to (Pw) that he spends considerable time in Perception and Discovery to the analysis of seeing that expressions. However, it is highly debatable whether an analysis of syntactical structure logically entails evidence for (Ps). Such an entailment already presupposes a particular theory regarding the relation between language and perception. Hanson’s thesis that linguistic structure determines the structure of perceptual experience would in turn require independent support. Obviously one cannot at this point simply resort to perceptual studies (which would only establish (Pw) at the most) nor to metalinguistic considerations without falling into circularity. Given this dilemma, Hanson’s particular arguments for (Ps) are in my opinion rather tenuous and inconclusive.

In passages reminiscent of Perception and Discovery, Kuhn also talks about visual gestalts and the “ rich body of psychological literature ” sup- porting (Pw). This literature strongly suggests to Kuhn that “ something like a paradigm is prerequisite to perception itself ” and that previous visual- conceptual experience shapes present perceptual experience. Like Hanson, however, Kuhn also recognizes that empirical studies only provide support for (Pw), and that (Pw) is neither necessary nor sufficient for establishing (Ps). As Kuhn writes,

though psychological experiments are suggestive, they cannot, in the nature of the case, be more than that. They do display characteristics of perception that could be central to scientific development, but they do not demonstrate that the careful and controlled observation exer- cised by the research scientist at all partakes of those characteristics (14).

Kuhn goes on to argue that what is required is indirect behavioral evidence rather than first-person psychological reports “ that the scientist with a new paradigm sees differently from the way he had seen before” (15). The “indirect and behavioral evidence” Kuhn offers is from the history of astronomy and physics and from certain psychological studies of perception. Consequently, though Hanson and Kuhn argue for (Ps), their respective ways of doing so are quite different. Where Kuhn looks toward paradigm shifts in the history of science, and how such shifts entailed perceptual shifts, Hanson options for (Ps) by an analysis of the logic of obersvation concepts. Kuhn is certainly aware of Hanson’s discussion of visual gestalts and psychological studies of perception (16), though he unfortunately pays little attention to the latter’s analysis of “ seeing ”, “ seeing as ”, and “ seeing that ” concepts. Consequently, where Hanson dismisses attempts to construct a neutral-observation language as a violation of the logic of observation concepts, Kuhn


rejects the neutral-language thesis as inconsistent with the experimental literature on perception and with the effects of paradigm shifts on perception in the history of science! Thus, when Kuhn states that an attempt to construct a neutral-observation language already “ presupposes a paradigm, taken either from a current scientific theory or from some fraction of everyday discourse ’’ (17), it is far from clear whether this attempt is psychologically impossible or logically impossible (that is, violates the logic of observation concepts). On the basis of Kuhn’s counter arguments to the neutral-language thesis, all of which counter examples are either drawn from the history of science or from psychology, it seems to me that nothing more than (Pw) has been established. For this reason, though I disagree with Hanson’s particular attempts to justify (Ps), the latter’s analysis and defense of both the weak and the strong versions of (P) is far deeper and more instructive than any argument to be found in Kuhn for the simple reason that psychological and historical evidence are not sufficient to establish (Ps). Unfortunately, this difference between Hanson and Kuhn has seldom been noted in the literature.

I will now attempt to defend thesis (a): There are theory-neutral observation statements. I will argue that (Q) is quite different from, though compatible with either (Pw) or (Ps), that is, that there are no theory-neutral knowledge claims. Clearly, the compatibility of (P) and (a) hinges on a distinction between knowledge claims and observation statements. Observation state ments (“ I now see, or did see, X ”) can either be reports of seeing as discriminating or seeing as interpreting. The latter type of observation statement requires background information, previous knowledge, and is paradigm- dependent or at least paradigm-influenced. The question is whether observation statements in the former sense, as reports of seeing as discriminating, are theory- or paradigm-neutral. I will argue that there clearly are cases where this occurs. I will argue that the paradigm case for such observation reports is the distinction between figure and ground, and the discrimination of changes in the figure-ground relation; e. g., discrimination of a change in movement, direction, size, or luminosity of a figure relative to its background. In other words, when one is describing or discriminating a figure X relative to a background Y , rather than describing some property or feature of X per se, then our observation report or description of X is theory-neutral. The paradigm case in the laboratory of such a theory-neutraI observation statement is the pointer reading, that is, discriminating the movement of a pointer relative to its background (the dial face, another pointer, an inscribed vertical line, etc.).

Hanson clearly fails to draw this distinction between two types of observation reports and thereby mistakenly collapses seeing as discriminating into seeing as interpreting. For example, the gestalt shift from glob to bacillus,

152 Paul Tibbetts

from bird to antelope, and from glass and wires to x-ray tube, are shifts in interpretation, not shifts in figure-ground discrimination. Regardless of one’s background knowledge, I contend that any one of these objects or figures could be discriminated relative to a background, although to recognize the positive terminal of a perceptual object (the wire and glass figure) is something quite different. Similarly with the other figures mentioned above. Regarding Hanson’s discussion of the Necker cube (18), which I agree is a prime example of a gestalt shift, one can discriminate this figure as ‘inter- secting straight black lines relative to a background ’ without seeing (recognizing) the figure as a Necker cube or even as a geometrical figure.

With this in mind, let us briefly examine Hanson’s classic example of the Ptolemist and the Copernican watching the sun rise. We cannot simply ask them, “ What do you see? ” as Hanson does, but rather “ What do you discriminate? ” The recognition question will elicit two different responses (“ The sun rising ” or “ The earth moving ”), whereas the discrimination question will (or should) elicit, “ The earth and sun pulling apart relative to one another ”. I fail to see how this latter observation report is theoretically- laden or paradigm-dependent, for how is discriminating a gap widening between two objects or two surfaces different from discriminating a pointer moving relative to a base-line on a dial? If observation reports concerning figure-ground relations are paradigm cases of seeing as discriminating, as I contend, then thesis (a) is at least plausible. However, I would not want to claim that observation reports concerning figure-ground relations constitute knowledge claims for the following reasons. Individual knowledge claims are contingent on background information as well as on future expectations. For example, to see X as a book requires some degree of familiarity with the cul- tural significance of objects of this sort; a number of expectations are also postulated, such as, “ If I open this object I expect to see words, figures, etc.. ” An observation report concerning a discrimination requires neither background knowledge (for example, that meters are scientific instruments), nor does it set up a hypothetical such as, “ If I do so and so to X than I will expect such and such consequences ”. (The convergence between this account of knowledge claims with C. I. Lewis’s position will be obvious to some readers.) When discriminating, in contrast with interpreting and recognizing, one simply pays no attention to future expectations regarding X, or the relation between X and Y.

Interestingly, both Hanson and Kuhn suggest in places a distinction such as I have attempted above, though they fail to develop its implications to any extent. For example, in Perception and Discovery Hanson talks about “ phe-


nomenal seeing ” or “ pure-visual-experience seeing, ” which he argues does occur apart from seeing as and seeing that.

Here the data before us are wonderfully confused. The researcher is usually clueless as to the nature of the phenomenon before him. He may not know what he is looking at, and so he can neither see it as a certain kind of phenomenon nor see that were he to perform in certain ways with respect to it, it would in turn perform in certain ways. (19)

He goes on to add that such phenomenal or pure observation is posterior, both temporally and logically, to seeing as and seeing that and requires considerable training to acquire. The advantage of phenomenal seeing is that “ By thinking of ourselves as research cameras for a period we may acquire what the camera lacks, vision into the workings of nature ” (20). This is a far cry from the position developed in his earlier book, namely, (Ps)! (On this matter of phenomenal or pure observation, Hanson was groping toward a phenomenology of perception not unlike what Peirce had in mind, that is, a phenomenology which “ just contemplates phenomena as they are, simply opens its eyes and describes what it sees ” (CP 5.37) Anticipating Hanson, Peirce also argued that such “ pure visual seeing ” required considerable perceptual training not unlike that found in the visual arts (CP 5.42) Unfortu- nately the convergence between these two thinkers cannot be further developed here.)

I fail to see any significant difference between seeing as discriminating and Hanson’s notion of phenomenal or pure-visual-experience seeing. Per- haps Hanson did come to recognize a difference between observation reports (concerning discriminations) and knowledge claims, and that (Pw) and even (Ps) are compatible with (a). Unfortunately, Hanson never developed his suggestive remarks concerning pure-visual seeing beyond the form they appear in above. In any case, it is important to recognize that his later book, Perception and Discovery, is fairly radical from the point of view of his Pat- terns of Discovery, recognizing as it does the distinction between phenomenal experience and theory-laden knowledge claims about such experience. Corre- sponding to Hanson’s phenomenal seeing is Kuhn’s recognition of the “ immediate experience ” from which operations and measurements are partly derived (21). Though no further reference is made by Kuhn to “ immediate experience ”, this particular passage does suggest that he might have been sympathetic to the discrimination-interpretation distinction drawn earlier regarding observation statements. But this is of course highly conjectural.

To summarize the above argument: a distinction can and should be drawn between two types of observation statements, one reporting what is

154 Paul Tibbetts

discriminated, the other what is recognized or interpreted. The first type of observation report would correspond to observation statements proper; the second type to knowledge claims. Where observation statements are theory- neutral in the sense of presupposing no background information or reference to future contingencies, knowledge claims are theory- or paradigm-dependent. Consequently, I agree with Hanson and Kuhn regarding (Pw), although I do have reservations concerning (Ps). In any case, whether (Ps) is justifiable or not, both (Pw) and (Ps) are to be distinguished from thesis (a) regarding theory-neutral observation statements. The failure on the part of Hanson and Kuhn to systematically develop this distinction beyond a few brief allusions to " phenomenal seeing ", " pure-visual-experience seeing ", and " immediate experience " has only served to reinforce the view of some philosophers that the discrimination-interpretation distinction (along with the seeing, seeing-as distinction) is empirically empty and conceptually unjustifiable. In turn, the defense of (P) appears to entail the rejection of thesis (a). The position I have argued for, on the contrary, is first of all that (Pw) and (Ps) are quite different claims, the one being contingently true, the other synthetic a priori; secondly, that empirical evidence for (Pw) is neither necessary nor sufficient to justify (Ps); thirdly, that (P) and (a) are essentially different theses, as seen from an analysis of the concepts " knowledge claim " and " observation statement "; finally, I have argued that Hanson, and to a lesser extent Kuhn, explicitly recognized, especially in his later writings, that (P) and (a) are not mutually exclusive and that the concept " observation report " has been uncritically collapsed to that of " knowledge claim ".

Department of Philosophy University of Dayton Dayton, Ohio 45469

REFERENCES

(1) B.Russel1, Our Knowledge of the External World (New York: Mentor Books,

(2) W. James, The Principles of Psychology (New York: Dover Books, 1910; 1958),

(3) N. Hanson, Patterns of Discovery (New York: Cambridge University Press, 1958),

(4) Ibid., p. 19. (5) N. Hanson, Perception and Discovery (San Francisco: Freeman, Cooper and CO.,

(6) T. Kuhn, The Structure of Scientific Revolutions (Chicago: University of Chicago

(7) Ibid., p.. 127.

1929; 1960) pp. 57-58.

vol. 11, p. 7.

p. 10.

1969), p. 169.

Press, second edition, 1970), p. 126.


(8) 1. Lakatos and A. Musgrave (editors) Criticism and the Growth o f Knowledge

(9) N . Hanson, Patterns of Discovery, op. cit., p. 181. (New York: Cambridge University Press, 1972), p. 198.

(10) Ibid., pp. 17-18. (11) Ibid., p. 24. (12) N. Hanson, Perception and Discovery, op. cit., p. 169. (13) Ibid., p. 158. (14) T. Kuhn, The Structure o f Scientific Revolutions, op. cit., p. 113. (15) Ibid., p. 115. (16) Ibid., p. 113. (17) Ibid., p. 127. (18) N. Hanson, Patterns of Discovery, op. cit., p. 21. (19) N. Hanson, Perception and Discovery, op. cit., p. 150. (20) Ibid., p. 151. (21) T. Kuhn, The Structure of Scientific Revolutions, op. cit., p. 126.

Dialectica Vol. 29, No 2-3 (1975)

Documents

«Hanson and Kuhn on Observation Reports and Knowledge Claims»