The rise of epistemic modal verbs in German

Modal verbs in epistemic reading are widely used in German. A general question with epistemically used modal verbs is, whether the epistemic reading developed out of the deontic usage by a grammaticalization process, or the epistemic and deontic usage arose simultaneously. The paper concentrates on modal verbs governing a past infinitive (e.g. sie muss das gesehen haben ‘she must have seen it’ in the sense of ‘I am sure that she saw it’). A corpus study searching for such combinations in Middle High German, Early New High German and New High German texts showed that the epistemic reading developed out of the deontic reading between the 14th and 16th century. A trigger for the epistemic reading might have been that the combination of modal plus past infinitive was available in the language as early as Middle High German, but with a different meaning, namely the one expressed by Ersatzinfinitiv constructions in Modern German (e.g. sie hat das sehen müssen ‘she must have seen it’ in the sense of ‘she was obliged to see it’). The Ersatzinfinitiv becomes frequent at about the same time as the unambiguous epistemic readings come about, so it is argued that after the advent of the Ersatzinfinitiv, speakers tried to attach some sensible meaning to the modal plus past infinitive complexes still lingering on, eventually settling for the epistemic reading of the modal.