Almost 200 years of attention to Indo-European linguistics has resulted in capable handbooks that treat the various components of grammar and also the lexicon. These handbooks have been guided by theoretical views that were established at various periods, and applied by subsequent linguists, often with little further consideration. As indicated repeatedly, the basic theoretical tool in Indo-European linguistics, as in all historical linguistics, is the comparative method. With it Indo-Europeanists have achieved notable results, including impressive reconstruction of the proto-language and some explanation of its patterning. The earlier chapters have exam ined the results, with special attention to the theoretical views under which they were achieved.