Semantic change through the discursive strategy of justification: The grammaticalization of the Japanese connective datte

•Meaning shift from 'but' to 'because' in the Japanese connective datte.•The role of the discursive strategy of justification in subjectification.•The increased co-occurrence of a reason expression, such as kara 'because.'•The role of preference organization of conversation in semantic change.

This study examines the process of subjectification by focusing on discursive strategy in the grammaticalization of the Japanese connective datte 'but/because'. It is found that datte shifted its meaning from 'but' to 'because' because it increasingly came to be used with justifications in new contexts of argumentative discourse. In the course of its development, the co-occurrence of an explanatory expression, such as -kara 'because', also increased, which further contributed to the entrenchment of the explanatory meaning. It is argued that the preference organization of conversation, which leads participants of conversation to avoid or mitigate face-threatening actions, motivated the semantic change from concessivity to causality.