Why words and co‐words cannot map the development of the sciences

A restricted set of full‐text articles from a sub‐specialty of biochemistry was analyzed and compared in terms of co‐occurrences and co‐absences of words. By using the distribution of words over the sections, a clear distinction among “theoretical” “observational,” and “methodological” terminology can be made in individual articles. However, at the level of the set this structure is no longer retrievable: Words change both in terms of frequencies of relations with other words, and in terms of positional meaning from one text to another. These results accord with Hesse's (1980) thesis about the sciences as fluid networks. The fluidity of networks in which nodes and links may change positions is expected to destabilize representations of developments of the sciences on the basis of co‐occurrences and co‐absences of words. The consequences for the lexicographical approach to generating artificial intelligence from scientific texts are discussed. © 1997 John Wiley & Sons, Inc.