The Negative Role of Empirical Stimulus in Theory Change: W. V. Quine and P. Feyerabend Jeu-Jenq Yuann Professor of Philosophy Department of Philosophy, National Taiwan University, 1
To all Participants of the 3rd GCOE International Symposium, We philosophers of science think that : 1. All scientists follow tools such as theories, models, mathematical formulations, apparatus, etc. without ever thinking what these tools are, or if they are wrong. 2. All scientific activities are conducted by reflecting empirical justifications which are accessible indirectly through these tools. 2
The indirectness here causes philosophical problems of various kinds. Among them, the most important one is this: How can we say that scientists do not follow their tools blindly? 3
W. V. Quine (1908-2000) and P. Feyerabend (1924-1994) 1994) shared many essential ideas in both historical as well as methodological contexts. Both claimed to be descended from the Vienna Circle. Both inherited the result of the protocol statements debates taking place in the Circle and took it as a crucial part of their philosophies. Both resorted to something like conceptual schemes by which they interpreted all experiences, even the most commonplace ones (the idea of ontology for Quine and the idea of theory for Feyerabend). 4
We begin first with Quine s view of science which is characterized by his generally conflicting allegiances to: A deterministic physicalism on the one hand and to A vision of inquiring man as active creator of his world, on the other hand. by S. G. Harding 5
Quine s philosophy of science is tolerant in the sense that it contains no rule for the normative nature of science. He offers a definition of science which merely stresses what science would not exclude rather than what it would exclude. As a consequence, there is no limit for the potential plausibility of theories; it would not be possible to define science in advance; nor to demarcate the difference between science and non-science. 6
Quine s philosophy of science as a version of pluralism; he says: But when I cite predictions as the checkpoints of science, I do not see that as normative. I see it as defining a particular language game, in Wittgenstein s phrase: the game of science, in contrast to other good language games such as fiction and poetry. A sentence s claim to scientific status rests on what it contributes to a theory whose checkpoints are in prediction. 7
Implausible contingencies might be very hard to believe, but science, insofar as an enterprise of fallibility and corrigibility, is ready to face them, as long as they hinge on checkpoints in sensory prediction. After all, Quine puts forward his naturalized epistemology as an integral part of science itself, without nonetheless presuming any possibility of delimiting science from whatever beyond science. 8
According to Quine s physicalism, empirical stimulus constitutes the evidence as the checkpoint of theory. Quine says: A stimulation σ belongs to the affirmative stimulus meaning of a sentence S for a given speaker if and only if there is a stimulation σ such that if the speaker were given σ, then were asked S, then were given σ, and then were asked S again, he would dissent the first time and assent the second. We may define the negative stimulus meaning similarly with assent and dissent interchanged. 9
However, continues Quine, stimulus meaning, by whatever name, may be properly looked upon still as the objective reality that the linguist has to probe when he undertakes radical translation. The objective reality Quine refers here serves practically an essential part of his idea of evidence in his philosophy of science. The evidence becomes clear in his exposition of observation sentences. 10
Due to their direct and firm association with our stimulations, observation sentences serve as initial links in connecting sentences within the frame of scientific theories. Because observation sentences can serve as means of verbalizing the prediction that checks a theory, we can say hence that to Quine, a scientific community is practically also a linguistic community whose members assent or dissent unanimously with regard to a sentence given in a stimulatory situation. 11
Observation sentences play their roles of evidence in science through theoretical hypotheses which, once formulated by observables, can be tested by experiments. The general character of theoretical hypotheses tested on the observational ground is called by Quine observation categorical. 12
A generality that is compounded of observables in this way Whenever this, that is what I call an observation categorical.. It is compounded of observation sentences It is a generality to the effect that the circumstances described in the one observation sentence are invariably accompanied by those described in the other. 13
Being an essential part of science, observation categorical links together theories projected to see what consists in the world and observations derived from the stimulatory situation. The link plays double roles of mediating the possibility of explaining the external world with the reference of empirical evidence. To Quine, so long as observational categorical is assured, the empirical content of theoretical hypotheses is thus safeguarded; so is the empirical status of science. 14
Quine is not keen to accept Popper s strict falsificationism because he is more inclined to accept holism under the influence of Duhem. Holism takes into account the theoretical context, rather than repudiating a theory on the basis of negative evidence exerted on its observation categorical. Theory change, however appeared to be banished from a straight confirmation or disconfirmation established on the basis of idealized observations. 15
Feyerabend examines the same problem of empirical stimulus. Phenomenologically what is given consists of the same things which can also exist unobserved it is not a special kind of object The given cannot be isolated by observation Following this statement I introduced the assumption that the meaning of observation statements depends on the nature of the objects described and, as this nature depends on the most advanced theories about objects, on the content of these theories. 16
In a word: observation statements are not just theory-laden but fully theoretical and the distinction between observation statements and theoretical statements is a pragmatic distinction, not a semantic distinction. 17
The theory has an inbuilt syntactical machinery that imitates (but des not describe) ) certain features of our experience. This is the only way in which experience judges a general cosmological point of view. Such a point of view is not removed because its observation statements say that there must be certain experiences that then do not occur It is removed if it produces observation sentence when observers produce the negation of these sentences. 18
Note two points from this citation: 1) that experiences would not be able to present themselves unless they are incorporated into a theoretical framework; 2) that a theory would stop us from see things beyond its range unless the supra- theoretical part of sensory experience hints its negation. Hence, pre-theoretical experiences, though theory-independent, are not arbitrators of the fate of a theory, but signs moving towards the removal of the theory. 19
About the idea of negation, Anscombe interprets Wittgenstein s Tractatus by saying: if we have a proposition, and insert a not into it, then what is being denied is exactly what the original proposition said. In negating a proposition we use the propositional sign to form another proposition, and we tend to feel that both say something: and hence want an account that would justify this feeling. Both propositions mention exactly the same things in the same relation to one another. 20
Feyerabend says this: But there is still human experience as an actually existing process, and it still causes the observer to carry out certain actions, for example, to utter sentences of a certain kind. Not every interpretation of the sentences uttered will be such that the theory furnishing the interpretation predicts it in the form in which it has emerged from the observational situation. 21
According to Feyerabend, with the understanding of the aim, we will then be able to understand why scientific theories play roles of such an importance in his philosophy. He says: This suggests that the methodological unit to which we must refer when discussing questions of test and empirical content is constituted by a whole set of partly overlapping, factually adequate,, but mutually inconsistent theories; in short, it suggests a theoretical pluralism as the basis of every test procedure. 22
Clearly, a crucial experiment [to the theory] is now impossible because there is no universally accepted statement capable of expressing whatever emerges from observation. What would emerge from observation? Human experience, answers Feyerabend. What would be the function of human experiences here? They function as something either beyond or beside the tenacity of the theory and cause the observer to utter certain sentences which do not match the predictions made on the basis of the theory. 23
This means that the observer, though uttering meaningful sentences on the basis of a theory, is still able to utter other sentences even without knowing another theory. What would be the function of these other sentences? They reveal the possible discrepancy between the physical order of the theory working as a cosmological point of view and the natural order of sensations. 24
The way to detect this fact is through the presence of experience which urges the observer to utter a sentence negating what the theory would predict in its tenacity. However, this negation does not hence imply whether the prediction sentences are true or false; all it says is the disagreement between the physical order of a theory and the natural order of sensations. 25
Feyerabend says: In order to be able to expand our field of action, the theory must guide us into new domains. It must also make us critical of our actions so that we may find out which actions are based on strong causal antecedents and which are not. Only the latter ones will be valuable indicators of external events. 26
Both the relevance and the refuting character of many decisive facts can be established only with the help of other theories that, although factually adequate, are not in agreement with the view to be tested Empiricism demands that the empirical content of whatever knowledge we possess be increased as much as possible. Hence, the invention of alternatives in addition to the view that stands in the center of discussion constitutes an essential part of the empirical method. 27
While both Quine and Feyerabend claimed to inherit the protocol sentence debates originated form the Vienna Circle, they differed at certain crucial point. When Quine proposed the core of science by referring to the sensory prediction established on the basis of stimulus meaning, Feyerabend diverged from Quine s approach at an important point. 28
Quine thought that the assent and the dissent regarding a stimulation held equal weight in deciding the nature of a global stimulus, but Feyerabend instead stressed the negative side of stimulation. It is mainly due to the negative role of empirical stimulus, Feyerabend was able to elaborate further the whole idea of observation sentences from a methodological point of view. 29
Thank You Very Much for Your Listening! 30