Lecture 14


Laudan on the Hierarchical Model of Justification

At the end of the last lecture, we briefly discussed Laudan's view that Popper, Carnap, and Kuhn all shared an assumption, i.e., that scientific justification is hierarchically structured. To review, Laudan thinks that Kuhn shares many assumptions with Popper and Carnap, in particular the view that science (and pursuit of knowledge in general) is hierarchically structured when it comes to justification. That is, we have the following levels of disagreement and resolution.

Level of Disagreement

Level of Resolution







According to Laudan, Kuhn disagrees with Carnap and Popper about whether scientists share the same cognitive values insofar as they are acting professionally (i.e., as scientists rather than individuals). If so, this would provide a way of resolving any dispute. Kuhn says No; Carnap and Popper (in different ways) says Yes. They both seem to agree that differences in cognitive values cannot be resolved. Thus, the reason Kuhn sees paradigms as incommensurable is simply that on his view there is no higher level to appeal to in deciding between the different values inherent in competing paradigms. Let us look at Laudan's description of the hierarchical model in detail.

Factual disputes, on the hierarchical view, are to be adjudicated by appealing to the methodological rules governing scientific inquiry.

Note that it is not a part of the hierarchical view that any factual dispute can be immediately adjudicated by application of methodological rules. For starters, the evidence may simply be inconclusive, or of poor quality. In that case, the rules would simply tell you to go find more evidence; they would also tell you what type of evidence would be needed to resolve the dispute. This does not mean, of course, that the evidence will be found. It may be impractical, or maybe even immoral, to go out and get evidence of the required sort. That, however, only means that some factual disputes cannot be settled as a practical matter; all disputes can be settled "in principle."

Methodological disputes, on the hierarchical view, are to be adjudicated by appealing to the goals and aims of scientific inquiry. The assumption is that rules of testing, experiment, statistical analysis, and so on, are not ends in themselves but means to achieving a higher goal.

On the hierarchical view of justification, axiological disputes cannot be adjudicated; there is no higher level to appeal to.

[Note: GOAL in subsequent discussion of hierarchical view is what it involves, and what it would take to refute it. Contrast with "Leibnizian Ideal."]

Factual Disagreement (Consensus)

Can all factual disputes be settled by appeal to methodological rules? There is a basic problem with supposing that they can. Although the rules and available evidence will exclude some hypotheses from consideration, they will never single out one hypothesis out of all possible hypotheses as the "correct" one given that evidence. In other words, methodological rules plus the available evidence always underdetermine factual claims. This may occur if the two hypotheses are different but "empirically equivalent," i.e., they have the same observational consequences. In this case, it is questionable whether the theories are even different theories at all (e.g., wave vs. matrix mechanics). In many cases we might think that the theories really are different, but observation could never settle the issue between them (e.g., Bohmian mechanics vs. orthodox quantum mechanics).

As noted earlier, this fact does not undercut the hierarchical model. The reason for this is that the hierarchical model only says that when factual disputes can be adjudicated, they are adjudicated at the methodological level (by applying the rules of good scientific inquiry). However, it is not committed to conceiving of methodology as singling out one hypothesis out of all possible hypotheses, but simply as capable, often enough, of settling a dispute between the hypotheses that we happen to have thought of, and giving us direction on how to gather additional evidence should available evidence be insufficient. That is, on the hierarchical model are rules simply answer the question:

Which hypothesis out of those available to us is
best supported by the available evidence?

The rules, then, do not tell us what hypothesis to believe ("the truth is h"), but simply which of two hypotheses to prefer. In other words, they provide criteria that partition or divide the class of hypotheses into those that are permissible, given the evidence, and those that are not. Thus it may turn out in particular cases that given the available evidence more than one hypothesis is acceptable.

Consider the following question: would it be rational for a scientist now, given our present state of empirical knowledge, to believe in Cartesian physics, or phlogiston theory, and so on? The point here is that though there are periods (perhaps long ones) during which the available rules underdetermine the choice, so that it is rationally permissible for scientists to disagree, there comes a time when rational disagreement becomes impermissible. That is, though whether a person is justified in holding a position is relative to the paradigm in the short term, in the long term it isn't true that just "anything goes." (Feyerabend, some sociologists conclude from the fact that "reasonable" scientists can and do differ, sometimes violently so, when it comes to revolutionary periods that there is no rational justification of one paradigm over another, that there is no reason to think that science is progressing towards the truth, or so on.)

How is this relevant to Kuhn? Well, Laudan claims that Kuhn is implicitly assuming that the fact that there is no neutral algorithm (methodological rule) that always tells us "This hypothesis is correct," and concludes from this that the choice between them must be, at least in part, non-rational. Then he concludes at the end of the book that this shows that science is not "progressing" towards the truth, considered as a whole. Progress can only be determined when the relevant and admissible problems (goals and aims of the discipline) are fixed by a paradigm. (Analogy with Darwinian evolution: no "goal" towards which evolution is aiming.) However, this may be true only in the short term. Laudan says (pages 31-32) that though "observational accuracy" might be vaguely defined, there comes a point at which it's apparent that one theoretical framework is more accurate observationally than another. Kuhn's problem is emphasizing too strongly the disagreement that can occur because of the ambiguity of shared standards.

Methodological Disagreement (Consensus)

What are some examples of methodological disagreement? Predictions must be surprising or of wide variety. Another example: disagreement over applications of statistics; statistical inference is not a monolithic area of investigation, free of disagreement.

Laudan says that goals and aims cannot completely resolve disputes over many methodological claims; there is underdetermination between goals and justification of methods just as there is between methods and justification of factual claims. For example, simply accepting that our goal is that scientific theories be true, explanatory, coherent, and of wide generality does not by itself determine which methodological principles we should seek.

This no more implies that methodological disputes cannot be resolved by appeals to shared goals than that factual claims can never be settled by appeals to shared methods. We can often show that a certain rule is one way of reaching our goal, or that it is better than other rules under consideration. Consider the rule that double-blind tests are better than single-blind tests. NOTE: This example already shows that the hierarchical model is too simple, since the lower-level facts influence what methods we think will most likely reach our goals of the truth about a subject matter.