Across languages, we find indefinites that trigger modal inferences. This article contributes to a semantic typology of these items by contrasting Spanish algún with indefinites like German irgendein or Italian uno qualsiasi. While irgendein-type indefinites trigger a Free Choice effect (Kratzer & Shimoyama, 2002; Chierchia, 2006), algún simply signals that at least two individuals in its domain are possibilities. Additionally, algún, but not irgendein, can convey that the speaker does not know how many individuals satisfy the existential claim in the world of evaluation. The authors contend that the two types of indefinites impose different constraints on their domain of quantification (irgendein and its kin are domain wideners (Kratzer & Shimoyama, 2002); algún is an 'anti-singleton' indefinite: its domain cannot be restricted to a singleton). This, together with the fact that algún does not require uniqueness, allows the authors to derive the contrast between irgendein and algún by using the pragmatic reasoning presented in Kratzer & Shimoyama (2002).