Summary The conceptof acute and transient psychoses is, together withthat of schizoaffective disorders, a challenge by the Kraepelinian dichotomy.Although

‘Nature does not take leaps,’ the scientist says, ‘There are always overlaps, bridges or something else in between.’ But why should Psyche – the most beautiful daughter of Physis (Nature) – take leaps, even when she is ill? ‘Because Emil Kraepelin decided so 110 years ago’, say some psychiatrists, and they add ‘The Kraepelinian dichotomy is – as we hope – well known to all of you’. Yes, of course the Kraepelinian dichotomy – or at least that is what some psychiatrists call it – is well known to all of us. But did Kraepelin really think dichotomously? Definitely not – at least not as dogmatically as his epigones. In fact Kraepelin thought the Kraepelinian dichotomy was only a fiction. Anyone can see this in one of his most famous papers, published in 1920, ‘Die Erscheinungsformen des Irreseins’ or ‘The manifestation types of insanity’ (Kraepelin, 1920). I have translated two of the more important parts of this paper into English as follows.