As is well known since Grimm (1837: 168, 949), Kolb (1964), Folsom (1968) and Scaffidi-Abbate (1973), the verb brauchen developed uses that are reminiscent of the modal verb müssen in formal and semantical respect, at least in negative polar environments. As the status of epistemic (nicht) brauchen has never been investigated in large-scale corpora, it remains contested to date how far it has gone in its grammaticalisation. Whereas some authors doubt that nicht brauchen has already grammaticalised into a fulfledged modal verb, claiming that it cannot be used in an epistemic manner, other studies discuss single authentic corpus examples of epistemic (nicht) brauchen. The overall aim of this study is to identify brauchen’s degree of grammaticalisation and investigate the morphosyntactic factors by which its potential is determined. Relevant conditions involve (i) the effect of a negation on a necessity verb, which according to some authors inhibits an epistemic interpretation (cf. Lyons 1977: 801 or Butler 2003: 984–989), (ii) the effect of the infinitive particle zu (cf. Reis 2001; 2005), which is omitted with brauchen in many spoken varietes making it more similar to müssen and (iii) lexical semantic features. Surprisingly, it turns out that the absence of an infinitive particle does not favour an epistemic interpretation, whereas it was shown that the presence of a negation makes an epistemic interpretation less likely with the closely related modal necessity verb müssen. The fact that epistemic brauchen occurs less than 200 times in the investigated corpora illustrates that it still has not developed a fully productive use for the majority of speakers. However, it turns out that there is a considerable number of speakers who used epistemic brauchen more than once and who account for almost 25 % of the occurences. This most likely to be caused by the lexical semantics of brauchen, which most typically involves a modal source located within its subject referent. Moreover, it appears that Reis’ (2001; 2005) concept of Strong Coherence is another obstacle for brauchen to develop a productive epistemic form.
