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Even if scientific concepts are worn out or seem obsolete, they are never definitively out of date. They can always return in subsequent theoretical conjunctures. This is due to the very particular nature of the concept, which is irreducible to positivist descriptions: concepts derive from experience and intend to explain this and represent departures from experience and its overviews. Anti-positivist epistemologists of the 20th century have been attentive to such philosophical characteristics. Their model of scientific conceptualisation is presented here and implemented for study of the concept of tendency. This shows that it survives to the period of its first formulation and that it deserves to return to contemporary psychophysiological debates.