In this book there is described a new and innovative hypothesis on the Proto-Indoeuropean verb system. Many unresolved issues of historical-comparative
reconstruction can find a straightforward solution in the light of this hypothesis; such as the origin of tense, mood, aspect, diathesis, etc. You will see that the original verb system was quite different from both the Hittite and the Greek one. Many verb categories, which were very important for the daughter languages, did not even exist in the protolanguage, and other categories, which were originally central to the protolanguage, have disappeared in all the descendant languages. In this regard, the key concept is the "control on action by the subject". This was what really mattered in the protolanguage.