Since new paradigms are born from old ones, they ordinarily incorporate much of the vocabulary and apparatus, both conceptual and manipulative, that the traditional paradigm had previously employed. But they seldom employ these borrowed elements in quite the traditional way. Within the new paradigm, old terms, concepts, and experiments fall into new relationships one with the other. The inevitable result is what we must call…a misunderstanding between two competing schools. The laymen who scoffed at Einstein’s general theory of relativity because space could not be “curved”—it was not that sort of thing—were not simply wrong or mistaken. Nor were mathematicians, physicists, and philosophers who tried to develop a Euclidean version of Einstein’s theory. What had previously been meant by space was necessarily flat, homogenous, isotropic, and unaffected by the presence of matter. If it had not been, Newton’s physics would not have worked. To make the transition to Einstein’s universe, the whole conceptual web whose strands are space, time, matter, force, and so on, had to be shifted. [Kuhn 1962: 149]
Kuhn’s argument for meaning incommensurability stems from two assumptions: 1) the theory dependence of observation and 2) holism.
1) On a traditional picture of science there is a distinction between the language of observation and the language of theory. The meaning of observation terms is given by their connections to experiences or sensations. The meaning of theoretical terms is defined by their connections to possible observation terms. But if no such distinction can be drawn, theoretical terms cannot be defined in terms of theory-neutral observation terms.
2) Instead, the meaning of theory-observation terms as a whole are given by their relations to all the other terms.
Hence when that whose system changes, the meaning of all the terms change. And thus different theoretical systems or paradigms cannot be compared by comparing their rival claims because they couched in different languages.
How can we challenge this argument? One initial worry is surely this. What if one makes a tiny change to just one equation in one theory in a paradigm? This will make a subtle change to the context of all the terms to which it interrelates and thus their meanings. But changes to them will change the context of the terms to which they relate and thus the meaning change spreads outwards through the paradigm. But does that really cause us any qualms? Does, in other words, anything follow from such a change in meaning?
Here are two suggestions for further thought.
Sense and reference
It is natural to think that the meaning of a word is just the thing it refers to: its reference. But if reference is all there is to meaning, then identity statements could not be informative eg Hespherus = Phosphorus, where these are names for the morning and the evening star both of which turn out to be Venus.
So Frege argued that words present their referents in different ways. The sense of a word is its mode of presentation of its referent. Words denote their referents but express their senses.
With this distinction in play, holism seems to apply to senses but not references. And since we seem able to cope with the idea of different senses for the same referent there seems no reason why this should not apply across paradigm changes.
Now one might argue that this works for little local variations of sense, for speakers who share some senses and differ only on some. In conversation they can perhaps work out that they are both thinking of the same person by different names. But perhaps, the Kuhnian defender argues, that only works where there has not been a radical change across many senses. What happens if in a paradigm change the meanings change much more and more radically?
Scheme-content dualism
Putting aside his dark talk of scientists living in different worlds, Kuhn’s picture of meaning-incommensurability seems to trade on the idea that the same world can be described in radically different ways. The same worldly content can be carved up by different conceptual schemes.
But this idea is attacked by Donald Davidson in his paper ‘On the Very Idea of a Conceptual Scheme’. The idea of dividing up the world like this is incoherent. The mark of a language, of a way of carving up the world, is that we can translate it. So the idea of a scheme true by its own standards but untranslatable is incoherent.