I. Recap of Kuhn

Last time we saw Kuhn’s theory about the nature of scientific activity. He thinks that science goes through a series of revolutions interspersed with periods of “normal science” where the paradigm within which scientists are working is taken for granted and not subject to testing.

II. Challenges to Kuhn

Kuhn’s theory about scientific revolutions has been criticized for leaving rationality out of the picture. Philosophers have made the following claims about Kuhn’s theory:

•   Kuhn thinks paradigm choice is a matter of mob psychology.

•   Kuhn thinks that paradigm choice cannot be based on good reasons of any kind.

•   Kuhn thinks that debates about paradigm choice amongst scientists involves mere persuasive displays without deliberative substance.

Kuhn was shocked by these claims. But there are some pretty good reasons that these were the conclusions his readers came to about his theory.

III. Some details of Kuhn’s view

Here are some of the details of Kuhn’s view that led others to make the above claims about it.

1.   Progress in science

When there is a shift from one paradigm to another, Kuhn cannot say that science has progressed. Why? Kuhn doesn’t think that one paradigm is better than another. The new paradigm is just different. The reason we can’t say that one paradigm is better than another, according to Kuhn, is because the means by which we might evaluate the new and the old paradigms is itselfparadigm dependent. He didn’t think that there was some neutral perspective from which to judge between paradigms. This leads us to the next claim.

2.   Incommensurability

Kuhn thought that paradigms are incommensurable. Two things are incommensurable if there is no common        standard of measurement to compare them. That is, Kuhn thought while people might argue in favor of one        paradigm or another, they would be doing so from within aparadigm. If it were possible to see this argument from outside any paradigm (from above) it would be clear that those engaged in argument are actually talking past each other. There are two kinds of incommensurability that are relevant here: incommensurability of meaning or          incommensurability of standards.

a.   Incommensurability of meaning

People debating paradigms may not be able to fully understand each other because the meanings of their words are slightly different. People operating within two different paradigms might seem to use the same word, but the meanings of these words might differ slightly. This version is less plausible than the other  kind. We would expect to see some evidence of this in the history of science.

b.   Incommensurability of standards

Kuhn argued that paradigms have their own standards for what counts as good evidence or a good argument and that these standards change across scientific revolutions.

3.   Theory-ladenness of observation

We might hope that the methods of science (e.g., observation) might permit us to get an unbiased attitude from which to adjudicate between two paradigms. But Kuhn argues that observation is not a neutral source of information for choosing between theories, science what people see is influenced by their paradigm. This is known  as the theory-ladenness ofobservation. The theory-ladenness of observation refers to the claim that observation cannot function as an unbiased way of testing theories (or paradigms) because observation is affected by the theoretical beliefs of the observer.

IV. Relativism

Kuhn’s claim that paradigms are incommensurable is largely responsible for others viewing his theory as a form of  relativism. Relativism is a complex topic. For our purposes, we will use the following definition. A view is relativist if it holds that the truth or justification of a claim depends on one’s situation or point of view. You can be a global    relativist, which would be the view that all truth (or justification) is relative. Or you can hold a relativist view about a more restricted domain such as art or morality.

Many people have interpreted Kuhn’s view about science as relativistic about standards governing reason, evidence and justification of beliefs. Kuhn himself denied that his view was relativistic in a serious way. Some claims in his   writing (e.g., incommensurability) seems relativistic, but other claims seem to dispute this. It may be that his views  can’t be fit together into a coherent whole.

V. Kuhn and theory Choice

Theory choice is a problem in the philosophy of science. The problem is to understand how scientists should choose between competing theories.

Remember that Popper had trouble finding a way to allow for rational decisions about theories. Kuhn has a similar problem, but he isn’t worried by it quite like Popper.

Kuhn claims that there are characteristics of a good scientific theory and that these criteria are shared amongst scientists.

The characteristics of a good scientific theory:

1.   Accuracy: the results that are deducible from a theory should be in agreement with the results of existing experiments and observations.

2.    Consistency: a theory should be consistent both internally but also with currently accepted theories.

3.   Broad-scope: a theory’s consequences should extend far beyond the particular observations it was initially designed to explain.

4.   Simplicity: a theory should bring order to phenomena that in its absence would be individually isolated and, as a set, confused.

5.   Fruitful: a theory should disclose new phenomena or previously unnoted relationships.

Kuhn claims that these values are shared amongst scientists, and therefore constitute a kind of objectivity. However, Kuhn argues that these criteria on their own can’t determine scientific choice. First, there will not always be agreement about whether a theory satisfies these criteria or to what extent. Second, there will be disagreement about how relatively important each feature of a theory is.

Kuhn thinks that choices between theories, despite shared ideas about the characteristics of a good scientific theory, will depend, in part at least, on idiosyncratic factors dependent on the biography and personality of the chooser. However, Kuhn doesn’t think that this makes theory choice irrational or illegitimate.

VI. Contexts of discovery and justification

Kuhn thinks that some philosophers of science might concede that he is correct that though subjective features might play a significant role in the discovery or invention of new theories, but will still maintain that objectivity enters into the picture in the process through which theories are tested, justified and judged.

The idea is that there is a significant difference between the context in which a theory is discovered or invented and the context in which a theory is tested, judged and justified.