From clause to discourse marker: on the development of comment clauses

This paper proposes an alternative account for the development of comment clauses (e.g. I think, I mean, I admit), which differs from previous accounts centring on grammaticalization, pragmaticalization, or lexicalization. Based on the framework of Discourse Grammar and building on Heine et al. (2021a, b), it is argued that their development involves a stage of cooptation, whereby a text piece is transferred from the sentence level to the metatextual level of discourse processing thus acquiring new grammatical properties, viz. independence from the host clause in terms of meaning, syntax and prosody, metatextual function, and positional freedom. All these changes are hard to reconcile with grammaticalization. At the same time, however, grammaticalization does play a role in the process once cooptation has taken place, affecting mainly the internal form of coopted expressions. •The development of comment clauses involves an operation called cooptation.•Cooptation is responsible for some of the main grammatical features of discourse markers.•Once coopted, comment clauses undergo a grammaticalization process.•Cooptation represents an alternative to accounts centring on grammaticalization, pragmaticalization, or lexicalization.