Presentation on theme: "A Dialectical Model of Scientific Discovery and Inquiry University of Groningen Lecture Sept. 29, 2011 Douglas Walton Centre for Reasoning and Argumentation."— Presentation transcript:
A Dialectical Model of Scientific Discovery and Inquiry University of Groningen Lecture Sept. 29, 2011 Douglas Walton Centre for Reasoning and Argumentation University of Windsor, Ontario
8 PARTS: First Four Parts In the first part, a case study of scientific discovery of the cause of pernicious anemia is presented. In the second part, an argumentation scheme for argument from correlation to causation is introduced In the third part, formal models of dialogue of the kind used to analyze argumentation are explained. In the fourth part, the properties of a type of dialogue called the inquiry are explained.
Last Four Parts In the fifth part, a type of dialogue called discovery dialogue is introduced. In the sixth part, the transition from the discovery phase to the later proof phase is modeled as a dialectical shift. In the seventh part, it is shown on the notion of burden of proof is essential for inquiry. The conclusions are in the eighth part.
In 1923 George R. Minot and William P. Murphy sought a cure for pernicious anemia, a disease characterized by low counts of red blood cells. George Whipple had earlier found that the best treatment for anemic dogs was to feed them liver. Minot and Murphy tested this treatment on human patients, and found that it worked. They shared the Nobel Prize in 1934.
The Cure Worked but the Cause Was not Known Dr. William Castle noted that people with their stomachs removed often died because of anemia, and was led by a series of experiments to formulate the hypothesis that something in the stomach was related to the disease. As an experiment, he ate red meat, forced himself to vomit, and then had patients eat his regurgitated stomach contents. This revolting experiment led to scientific inquiry that proved that the substance necessary for red blood cell formation (found abundantly in liver) was vitamin B12.
(Walton, 2004) Abductive Reasoning Argumentation Scheme F is a finding or given set of facts. E is a satisfactory explanation of F. No alternative explanation E’ given so far is as satisfactory as E. ___________________________________ E is plausible, as a hypothesis.
Critical Questions (Walton, 2004) CQ1: How satisfactory is E itself as an explanation of F, apart from the alternative explanations available so far in the dialogue? CQ2: How much better an explanation is E than the alternative explanations available so far? CQ3: How far has the dialogue progressed? How thorough has the search been in the inquiry? CQ4: Would it be better to continue the dialogue, instead of drawing a conclusion?
Scheme for Argument from Correlation to Causation There is a positive correlation between A and B. Therefore A causes B. Evaluating causal argument is best carried in a dialogue format using critical questions.
Three Critical Questions Is there good evidence that the causal relationship goes from A to B, and not just from B to A? Can it be ruled out that the correlation is accounted for by some intervening factor? Can it be shown that the increase or change in B is not solely due to the way B is defined, or the way entities are classified?
The Causal Relation The causal relation is controversial to define, but it means something roughly like this. A is one of a set of conditions that are (when taken together) sufficient for the occurrence of B, and A is also a necessary condition for the occurrence of B. Also, A must meet some pragmatic requirements.
Inquiry The goal of the inquiry is to prove that a statement designated at the opening stage as the probandum is true or false, or if neither of these findings can be proved, to prove that there is insufficient evidence to prove that the probandum is true or false. The most important characteristic of the inquiry as a type of dialogue is the property of cumulativeness
A Case of Retraction in Inquiry Astronomer Andrew Lyne observed a pattern of periodically blinking stars, and concluded that this observation could only be explained by the postulation of the existence of a previously undiscovered planet (Walton, 1998, 71). After he re-examined his original analysis of the data, he concluded that it contained two small measurement errors that provided sufficient grounds for retracting his earlier hypothesis. It was an emotional moment when he had to admit his error at a scientific meeting. Initially the audience felt pity for him, but at the end of his talk the audience applauded, evidently acknowledging his honesty and courage that must have motivated such an admission.
C. S. Peirce on Inquiry Peirce advocated a fallibilism that admits of the susceptibility of scientific proof to error. On his view, even the most careful scientific inquiry might produce an outcome which could later be shown to be wrong (Peirce, 1931, 2.75). Peirce wrote that many things are “substantially certain” (Peirce 1931, 1.152), but that this is different from absolute certainty.
Peirce on Truth and Inquiry On his view truth is an aim of inquiry, and an important motive for scientific research, but to arrived at truth beyond all doubt would take an infinite amount of time. It was part of his view that the fixing belief by “tenacity” or “authority” blocks inquiry by implying claim that no further inquiry is necessary (Cooke, 2006, 34).
Popper on Inquiry The procedure of inquiry was seen by Popper (1962, 312) as a continuous movement of trial and error that proceeds by degrees of improvement, and that can reach an outcome that is provisionally acceptable. On his theory, even though a theory or hypothesis can be accepted as part of science, it must always remain open to falsification.
Bounded Procedural Rationality Popper held that scientific inquiry is based on an evidential procedure that moves toward truth and is independent of the knowing subject. Both Peirce and Popper viewed the inquiry as a procedure that uses evidence pro and con a hypothesis to move forward to tentative acceptance of a scientific theory or experimental finding, but is open to retraction.
According to the sequence of argumentation shown in the next figure, a standard of proof needs to be set at the opening stage. During the argumentation stage, evidence for and against the proposition is brought forward. As determined by the availability of time and resources, the sequence of argumentation must eventually be closed off.
Evidence and Standards of Proof Employed in an Inquiry
Discovery Dialogue Discovery dialogue (McBurney and Parsons, 2001, 5) moves through ten stages (McBurney and Parsons, 2001, 5) called open dialogue, discuss purpose, share knowledge, discuss mechanisms, infer consequences, discuss criteria, assess consequences, discuss tests, propose conclusions, and close dialogue. The participants open the discussion, share knowledge by presenting data items to each other, build arguments by inferring consequences from data items, discuss criteria for assessment of consequences presented, assess the consequences in light of the criteria, pose one or more conclusions for possible acceptance, and close the dialogue. The stages of the discovery dialogue may be undertaken in any order and may be repeated (2001, 6). However, they don’t at least directly consider how their model might be applied to scientific discovery
Burden of Proof The burden of proof at the closing stage in a discovery dialogue is different from the way burden of proof works in an inquiry dialogue. In an inquiry, the aim is to avoid retraction insofar as this is possible, and therefore a high standard of proof needs to be set. The conclusion accepted in a discovery dialogue is much more and conjectural nature.
BoP in Discovery Dialogue A hypothesis may be tentatively accepted even though the evidence supporting it is slight, provided there is no evidence against it, and there is no competing hypothesis more strongly supported by the evidence. The aim of a discovery dialogue is not to prove something to a high standard, but only to provide a hypothesis that enables an investigation to move forward by collecting more evidence that will be useful in an inquiry dialogue, once the evidence that has been amassed is sufficient to justify opening an inquiry.
Dialectical Shifts A dialectical shift occurs in cases where, during a sequence of argumentation, the participants begin to engage in a different type of dialogue from the one they were initially engaged in (Walton and Krabbe, 1995). In the following classic case often cited as an example, two agents are engaged in deliberation dialogue on how to hang a picture. Engaging in practical reasoning they come to the conclusion they need a hammer, and a nail, because they have figured out that the best way to hang the picture is on a nail, and the best way to put a nail in the wall is by means of a hammer. One knows where a hammer can be found, and the other has a pretty good idea of where to get a nail. At that point, the two begins to negotiate on who will get the hammer and who will go in search of a nail. In this kind of case, we say that the one dialogue is embedded in the other (Walton and Krabbe, 1995),
We Can Use Argument Mapping Tools like Rationale
The Carneades Argumentation System Gordon and Walton (2009) have defined an abstract formal model of argumentation called Carneades that works as a theory and proof construction process for making justified decisions that can be applied to scientific as well as legal argumentation. In the model, four standards of proof are formulated as shown on the next slide. It is assumed that there can be pro arguments as well as con arguments with respect to a claim. It is also assumed that arguments can be comparatively weighed so that one argument is said to be stronger than another based on the evidence for and against each of the arguments.
Carneades: Standards of Proof The scintilla of evidence standard is met iff there is one argument supporting the claim. The preponderance of the evidence standard is met iff scintilla of evidence standard is met and the weight of evidence for the claim is greater than the weight against it. The clear and convincing evidence standard is met iff the preponderance of the evidence standard is met and the weight of the pro arguments exceeds that of the con arguments by some specified threshold. The beyond reasonable doubt standard is met iff the clear and convincing evidence standard is met and the weight of the con arguments is below some specified threshold.
Carneades and Critical Questions Carneades has an argument mapping tool. Critical questions are modeled by Carneades as additional premises corresponding to the critical questions of an argumentation scheme. In the Carneades system, critical questions matching an argument are reformulated as three types of premises called ordinary premises, assumptions and exceptions (Gordon and Walton, 2009). Assumptions are assumed to be acceptable unless called into question. Exceptions are modeled as premises that are assumed to be not acceptable, and can undercut an argument if found to be acceptable.
How Carneades Models Critical Questions for a Causal Argument
Premises of Argument from Correlation to Cause (Carneades)
The Argumentation is Evaluated in a Dialogue Using Burdens of Proof Evaluating argumentation in a case is a matter of adjusting burdens of proof adjudicated at different stages of the dialogue. During the argumentation stage, as speech acts like arguments are put forward, they need to be evaluated in light of how the burden of proof shifts from one side to the other. For example if a claim is made, and the other party challenges the claim, the first party has to support its claim with an argument or else he has to retract the claim. There is also a global burden of proof set at the opening stage, that determines how strong the argumentation on each side needs to be in order to be successful in the dialogue.
Conclusions 1 The argumentation in the pernicious anemia case naturally breaks down into two dialogues. During the discovery dialogue, the feeding-of- liver treatment on human patients worked. Argument from correlation to cause was the warrant for drawing an inference to a causal hypothesis between these two sets of events.
Conclusions 2 Later experiments, showed that a deficiency of vitamin B12 was the cause. Only at this stage was an explanation given at an adequate theoretical level to prove the hypothesis about the cause of the disease and answer all the critical questions. The investigation shifted to an inquiry dialogue where enough evidence to prove that deficiency of vitamin B12 was the cause.
Conclusions 3 Traditional philosophy of science had drawn a bright line between two stages, a discovery stage and later proof or justification stage. The recent climate of opinion goes towards the view that there is a continuous sequence of argumentation from the one stage to the other. The conclusion of this paper seems to support the latter view more strongly.
Some References Black, E. and A. Hunter, (2007). A Generative Inquiry Dialogue System, Sixth International Joint Conference on Autonomous Agents and Multi-agent Systems, ed. M. Huhns and O. Shehory, 1010-1017. Cooke, E. (2006). Peirce’s Pragmatic Theory of Inquiry: Fallibilism and Indeterminacy. London: Continuum. Gordon, T. F. (2010). The Carneades Argumentation Support System, Dialectics, Dialogue and Argumentation, ed. C. Reed and C. W. Tindale, London: College Publications. Gordon, T. F., H. Prakken and D. Walton (2007). The Carneades Model of Argument and Burden of Proof, Artificial Intelligence, 171, 875-896. Gordon, T. F. and Walton, D. (2009). Proof Burdens and Standards, Argumentation and Artificial Intelligence, ed. I. Rahwan and G. Simari, Berlin: Springer. Jacovino, N. (2009). Red-Blooded Doctors Cure Anemia, The Harvard University Gazette, January 22, 1998. Found Feb. 3, 2009 at: http://www.news.harvard.edu/gazette/1998/01.22/Red-BloodedDoct.htmlhttp://www.news.harvard.edu/gazette/1998/01.22/Red-BloodedDoct.html Josephson, J. R. and Josephson, S. G. (1994). Abductive Inference: Computation, Philosophy, Technology. NY: Cambridge University Press. McBurney, P. and Parsons, S. (2001). Chance Discovery Using Dialectical Argumentation, New Frontiers in Artificial Intelligence, ed. T. Terano et al. (Lecture Notes in Artificial Intelligence, vol. 2253). Berlin: Springer, 414-424. Peirce, C. S. (1931), Collected Papers. Edited by C. Hartshorne and P. Weiss. Cambridge: Harvard University Press. Popper, K. (1962). Conjectures and Refutations: The Growth of Scientific Knowledge. Routledge: London. Walton, D. Abductive Reasoning. Tuscaloosa: University of Alabama Press, 2004.