In the course of their history, notably when borrowed from a foreign field, scientific terms and concepts undergo transformations which seem to follow a law of “ontological lightening”, going with a loss of their theoretical background. The paper gives instances of this in Tesnière, Bühler and Koschmieder, focusing on the relations between psychology and linguistics. In Koschmieder, the “case of coincidence” (= performativity in his terminology) is bound with a grammatical issue (the use of Slavic aspect), and a theory of cognition borrowed from the Psychology of Thought. This suggests that concepts are incorporated in “argumentative sequences”. Thus the paper draws an analogy between mechanisms in lexical truncations and in terminology. Context truncations do preserve he “reference” of the concepts (that is to say empiric identification procedures), but not their “signified” (their relations with other concepts in a specific theoretical context).