This dissertation concerns the semantics of free choice indefinites, indiscriminatives (Horn, 2000), and the derivational relationship between these two indefinite classes across languages. It defines indiscriminatives as indefinites that occur under negation to express the specificity or noteworthiness of a yet to be revealed candidate for satisfaction of a predicate. They include English indefinites of the 'just any' paradigm, as well as its translations across languages. The dissertation refutes the prevailing attitude in the literature that indiscriminatives are pragmatic enrichments on free choice indefinites that are unessential to understanding free choice phenomena, and it proposes a novel semantics that predicts that free choice indefinites are actually frequently derived from indiscriminatives. Two case studies are considered: English indiscriminative 'just any' and bare 'any', as well as indiscriminatives in Cuevas Mixtec, an Otomanguean language of southern Mexico. In both languages, indiscriminatives may have free choice readings, and in Cuevas Mixtec, an optional focus particle 'va' must be attached to the indiscriminative to derive a free choice indefinite. The proposal accommodates this data first by developing a novel analysis of free choice meaning, then by building a general semantics of indiscriminatives that may be modified to derive free choice indefinites. The proposal breaks down the meaning components of free choice indefinites and indiscriminatives into four semantic ingredients: existential quantification, the activation of subdomain alternatives, exclusive meaning, and an inferential operation called minimal sufficiency evaluation. Existential quantification and subdomain alternatives are involved in the semantic composition of both types of indefinite, and they are exploited in deriving polarity sensitive behavior more broadly by means of inferential conflicts between an assertion and its propositional alternatives (Krifka, 1995). For example, English indefinites of the 'any' paradigm are analyzed as existential quantifiers with a presupposition that some propositional alternative to their assertion, with a strictly more specific nominal restriction, is true. This results in an assertion that is inferentially weaker than the presupposition in upward entailing environments, and a felicitously stronger assertion in environments that reverse inferential strength relationships. Indiscriminatives additionally feature an explicit or implicit exclusive meaning component, modeled as the 'only' operator defined by Coppock & Beaver (2014). This operator applies an exhaustified interpretation on the assertion relative to propositional alternatives, and when negated, it forms an assertion that matches the presupposition in strength. Free choice indefinites instead feature minimal sufficiency evaluation, an operation that associates individuals with degrees on a relevant scale and imposes a dependency on exceeding some minimum degree suficient for satisfaction of a predicate. The operation reverses the inferential strength relationships between scalar terms in semantic environments with modal expressions, satisfying 'any''s need for a stronger assertion for felicity. These four semantic ingredients may be reorganized with respect to each other in order to account for distributional differences between polarity sensitive indefinites across languages. Most crucially, indefinites with both indiscriminative and free choice readings organize the ingredients so that the 'only' operator is interpreted with narrow scope with respect to minimal sufficiency evaluation, explaining the derivation of free choice indefinites from indiscriminatives.