The problem of non-being and intentionality has been among the topic subjects of Western philosophers from Parmenides to Quine. In medieval and post-medieval scholastics the issue was articulated mainly as ens rationis (a being of reason). The paper deals with the character and division of beings of reason in Francisco Suarez (1548 – 1617). An immanent critique of Suarez’s theory is given as well. The paper offers also a brief outline of the history of its later reception by Baroque authors.