On the semantic change of evidential argument jakoby-clauses in Polish

The main aim of this chapter is to examine the semantic change of evidential
argument clauses headed by the complementizer jakoby in the history of Polish.
Mainly, I argue that jakoby developed from a hypothetical comparative complementizer
meaning ‘as if’ into a hearsay complementizer, and provide empirical evidence
showing that this process happened in the late Old Polish period, i.e. around
1500. To begin with, I compare jakoby-clauses with complement że-clauses (‘that’-
clauses) at the syntax-semantics interface, elaborate on their selected differences,
and account for the source of these differences. Diachronically, I show that two
factors in the lexical meaning of jakoby were responsible for the semantic change
that it underwent: i) equative comparison and ii) counterfactual meaning. Both
factors are taken to have paved the way for inferences from reportative or hearsay
information and, simultaneously, for the compatibility with an informational conversational
background.