Regarded by Lacan as one of Freud's most central explanatory concepts, Nachträglichkeit was usually translated by Strachey as 'deferred action' (or some close variant). This is unsatisfactory because the idea of the delayed effect of an early trauma is often combined in Freud's usage with that of the retrospective reconstruction of the psychological significance of that trauma. Consequently, (1) translators have the problem of whether or how to signal this aspect of the concept—which the German does not suggest; (2) it has been thought that the concept implies a kind of 'backward causality' which challenges conventional notions of temporality. The authors dispute the latter (2) by construing the issues in terms of a cybernetic system and by appealing to parallel situations in ethology and developmental psychology where no such problems for causality are envisaged. With regard to (1), they make suggestions for possible English terms which reflect either the structure of the German word or the nature of the microtheory which it implies.