According to the Unaccusative Hypothesis (Perlmutter 1978) not all intransitive verbs share the same syntactic and argument structure, and can therefore be divided into two classes, unergative verbs and unaccusative verbs. This paper shows that in Slovene, like in many other languages, there exists a special class of unaccusatives which can participate in the causative alternation under certain conditions (when an externally caused event can come about spontaneously).
These verbs always come in two variants, transitive (Peter odpre okno ‘Peter opens the window’) and intransitive (Okno se odpre ‘The window opens’). The comparison with other languages reveals that Slovene alternating causative verbs exhibit all the crucial properties of this class of verbs. In Slovene the detransitivisation of causative verbs can be indicated by the cliticisation of the morpheme se (odpreti – odpreti se ‘open’), by the change of the vowel –i– into –e– in the infinitive stem (počrniti – počrneti ‘blacken’) or by the use of identical form of the verb (zmrzniti – zmrzniti ‘freeze’). The data, however, provide evidence that only reflexivisation is still productive in modern Slovene, while the other two processes are no longer employed to form new intransitive verbs from transitive causative verbs.