Taxonomy is a term meaning classification, as well as the study of the principles of classification.
Charles S. Peirce was interested in classification in both senses of the term. He and Ferdinand de Saussure (co-discoverer of modern semiotics) also devoted much of their attention to the classification of sciences.
For Peirce, semiotics is one of the three normative sciences (ethics and aesthetics being the other two) that are part of philosophy.
For Saussure, on the other hand, semiology (as he calls it) should be, when he was born, a branch of social psychology.
The different way in which Peirce and Saussure view the relations of sign theory to other fields of study is just one of the many differences in their approaches to this theory.
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