Many of the categories used in the discussion of the Indo-European verbal paradigm are functional rather than structural, a fact recognized and succinctly stated by Brugmann: ‘Bei der Gruppierung der Formen eines Verbalsystems ist die traditionelle Grammatik von der Bedeutung der Formen ausgegangen, nicht von formantischer Gleichartigkeit. Infolge davon hat sie zum Teil solches, was formal zusammengehört, voneinander getrennt und solches was formal verschieden ist, vereinigt.’ And later in the same paragraph: ‘Zunächst ist zu betonen, dass ein Bildungsunterschied zwischen den Formen des Präsenssystems und den Formen des Aorists ursprünglich nicht vorhanden war.’ Among his examples he points out the structural identity of the ‘imperfects’ Skt. ábhāt, Gk.
with the ‘aorists’ Skt. ásthāt, Gk.
, and the use of the stem *ĝene- to form an ‘imperfect’ in Skt. ájanat, but an ‘aorist’ in Gk.
Of course, it is the coexistence or the absence, as the case may be, of a ‘present’ built from the same stem that determines whether such a form is to be accounted an ‘imperfect’ or an ‘aorist’. All this is in sharp contrast to the procedure of Semitists, who, in their treatment of finite verbs, employ categories that are structural throughout; e.g. in Arabic grammars and dictionaries the various ‘stems’ are merely listed in an arbitrary numerical order. Thus, once past the ‘First’ or Ground-stem, the structural relations of all the other stems (II-XV) are throughout predictable; it suffices for the lexicon merely to mention which of these derivative stems exist, without quoting the actual forms. One can imagine the mild chaos created in Arabic grammar if a strictly functional classification of verb-stems as ‘reflexive’, ‘causative’, etc. were to be introduced.