The pseudo-verb hastan (to exist) has only simple present tense; in addition, it is truly and purely existencial only in the case of third person singular (hast). The fact is that the verb has been the product of this very case, as an "existential is", hast (he/she/it exists). For other persons the conjugation has to use enclitic copulas. These copulas are, in turn, derived from the declension of PIE *h1es- (to be); as if the predicative "to be" has been an auxiliary verb turned into enclitic, to provide six endings for 1st/2nd/3rd person (singular & plural). However, as it is said, the 3rd person singular has no ending in the case of hastan. That is to say that the existential hast (exists), which is like the alter-ego of the copula ast (is), takes no ending, while the present stem of all other verbs take an archaic ending -"ad" in their 3rd person singular.