This paper has argued that richness of the base, when combined with OT’s inherent commitment to typology, leads to an improved understanding of problems of indeterminacy in underlying representations. The controversy over the length of Arabic final vowels, a controversy to which many analysts have contributed without a final resolution, disappears once the phenomena are examined from the perspective of ROTB and a typologically responsible CON. It has been suggested (M. Hale and Reiss 1998: 660) that “the notion of richness of the base [is] a computational curiosity of OT grammars that may be quite irrelevant to human language”. This analysis of Arabic shows, on the contrary, that ROTB is fundamental to the theory and inextricably linked with the results that OT can achieve.