This article looks at two current models of feature geometry, the Halle-Sagey model as modified by Halle (2005) and the Clements-Hume model, from the perspective of palatalization and related processes in Polish, Russian, and Ukrainian. The Halle-Sagey model predicts that palatalization should be analyzed by assuming derivational levels and is thus at odds with the tenet of strict parallelism in Optimality Theory. In contrast, the Clements-Hume model appears to be able to achieve the same goal without recourse to derivational stages because it is based on the assumption that, in the ways relevant for palatalization, vowels and consonants are characterized by the same features. However, analysis of palatalization and related processes shows that this assumption is incorrect. The consequence is that derivational stages cannot be avoided and that the tenet of strict parallelism must be rejected.

This article argues against Burzio's (2001) reanalysis of Rubach's (2000b) glide and glottal stop insertion in the Slavic languages. It is shown that the reanalysis cannot account for the range of attested facts and that it leads to unwarranted extensions of Optimality Theory by relying on unrestricted targeted constraints. The conclusion is that Optimality Theory must admit derivational levels.

This article challenges the principle of strict parallelism in Optimality Theory by providing evidence that Duke-of-York derivations, deemed to be impossible by McCarthy (2002), exist in phonology. An analysis of two independent fragments of Polish phonology, chain shifts in velar palatalization and labial fission, shows multiple Duke-of-York effects because segment inventory constraints posit conflicting requirements for the well-formedness of outputs at different depths of derivation. It is concluded that Optimality Theory must permit constraint reranking and admit three derivational levels: two lexical levels and one postlexical level.

This article investigates glide and glottal stop insertion in Bulgarian, Slovak (two dialects), Polish (two dialects), and Czech. It is argued that Optimality Theory should be modified by introducing derivational levels and that OT auxiliary theories, in particular, output-output theory, MAX (Feature) theory, and sympathy theory, should be rejected.