Adverbial causal clauses as relative clauses: on siccome “because/since” from Old to Contemporary Italian

This paper investigates to what extent adverbial causal clauses and relative clauses can be reduced as one and the same phenomenon. Whereas causal clauses have always posed a challenge for a unified account of relativization and adverbial subordination in theoretical studies, typological research has long demonstrated that causal clauses are diachronically connected to relative clauses as well as to adverbial subordinates that have been analysed as relative clauses. We argue that at least some causal clauses are underlyingly relative clauses over situations (see Arsenijević 2021). Our claim is supported by the diachronic development of the Italian subordinator siccome ‘because/since’, an univerbated form morphologically composed of two items, the comparative-similative wh-pronoun come ‘how’ and the demonstrative adverbial pronoun sì ‘so’. We demonstrate that the causal subordinator is derived from the comparative-similative one via a three-stage diachronic change which is formally captured in terms of type of movement and null elements (Kayne 2005, Cinque 2020b). In so doing, our paper extends a relative clause analysis to causal clauses and adds a novel path to the diachronic development of causal clauses.