 If a theorist starts from a possible worlds framework, and comes under pressure to recognize hyperintensional distinctions, one response is to add impossible worlds (Priest 1992; Zalta 1997; Kiourti 2010; Jago 2015; Berto &amp; Jago 2019) taken as ways things could not be, or worlds where some truth of logic, mathematics, or metaphysics fails. We will be brief on this topic here, as one can consult the entry on  impossible worlds  for more details.