The revised Proto-Basque sound system presented in the preceding chapters uses methods of dialect comparison and internal reconstruction to arrive at new hypotheses concerning the segmental and prosodic structure of the language as spoken before the Common Era. The major differences between this reconstruction and earlier reconstructions of Michelena, Lakarra, and Trask are evaluated and discussed in this chapter, including the introduction of *ph into the consonant inventory; the analysis of *p, *t, *k as aspirated stops; arguments for a lone rhotic *r; arguments for *m as a proto-phoneme; and, in tandem, the reconstruction of only a single sibilant *s for Proto-Basque, and the existence of root-initial consonant clusters *sph, *sth, and *skh. Both the single sibilant hypothesis and the cluster hypothesis make Proto-Basque qualitatively different from the modern language and result, arguably, in a deeper reconstruction, where bigger word families are recognized and many internal relationships between words are established.