|Observation language: a language that does not use any terms of a theory and therefore would be neutral, is taken to be impossible by most authors. See also experiments, theoretical terms, theoretical entities, theories, descriptions.|
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Observational concepts/Millikan: we have much more of it than we commonly assume.
For them there are good tests - although they are fallible, which are independent of our theories.
Observation Language/Learning/Quine/Word and Object/W + O/Millikan:
If a general term is learned by induction from observation instances, these instances must be similar in two ways:
1. From the point of view of the learner, they must be sufficiently similar from time to time,
2. From different points of view. So that teachers and students can talk about the same.
E.g. "a square perpendicular to the line of sight" is nothing that can be shared by two people.
R. G. Millikan
Language, Thought, and Other Biological Categories: New Foundations for Realism Cambridge 1987