Ens rationis in Caramuel’s Leptotatos (1681) 71 Ens rationis in Caramuel’s Leptotatos (1681) Daniel Dominik Novotný The being of reason (ens rationis) belonged to one of the most con- troversial topics among the seventeenth century scholastic philoso- phers. Thus, an important contribution to this topic might be expect- ed from recently re-appreciated polymath Juan Caramuel Lobkowitz (1606–1682). This paper aims to investigate Caramuel’s last word on beings of reason in Leptotatos (1681). Caramuel is shown to be a criti- cal commentator of the debate among the Jesuits over the ontological status of impossible entities (as the sole species of beings of reason). Also, it is shown that the guiding idea of Caramuel’s approach to beings of reason might be called ‘the bewitchment by language’. In Caramuel’s own words, beings of reason are nothing but beings of language. Seventeenth century scholastic philosophy witnessed an explo- sion of debates over mind-dependent entities (entia rationis, beings of reason). The present paper aims to identify Caramuel’s contribu- tion to these debates in Leptotatos (1681). My procedure is as fol- lows: I will (I) give a summary of the content of the relevant parts of Caramuel’s Leptotatos; (II) explain his impossibilist understanding of what beings of reason are; (III) discuss the central difficulty of im- possibilism, which concerns the unity of beings of reason; (IV) briefly discuss Caramuel’s two novel ideas (the first concerns his refutation of the “ontological” argument for the existence of beings of reason, the second concerns the argument for the existence of God from the Caramuel.indb 71 Caramuel.indb 71 2.7.2008 11:00:52 2.7.2008 11:00:52