Optimality Theory has implications for a wide range of issues in linguistics and adjoining fields. The previous chapter dealt with phonological, morphological, and syntactic matters, though with the focus always on the theory and results deducible from it, rather than on the phenomena. This chapter offers a synoptic view of some of the discoveries and issues that have emerged as the scope of OT research has expanded into other areas. Its relatively modest goals will be fulfilled if it helps readers to situate the most important questions and results in relation to the rest of OT and if the bibliography leads some readers to delve more deeply into these matters.

Perhaps because OT was originally and most extensively illustrated with phonological phenomena, there is relatively little theory-internal disagreement about the answers to some basic questions as they apply to phonology: What is the input? What does GEN do, and what candidates does it offer up? How do faithfulness constraints work? How does a theory with violable constraints obtain absolute ill-formedness? But when these same questions are asked about syntax, a thousand flowers bloom and many schools of thought contend. Furthermore, syntactic applications of OT must address an issue that is somewhat less important in phonology (see §2.3): how is it possible to have optionality or variation when EVAL usually supplies a unique optimal candidate (§1.1.2)? These questions are the topic of §4.1.

From the outset, OT has been coupled to an explicit theory of learning. It has also figured prominently in empirical studies of language acquisition, again almost from the outset.