Throughout Calderón's career, the function of theatre in the service of self-imagination and critique is adjusted to a variety of specific needs, with greater or lesser success, depending on the dramatist's ability to incorporate the forms of the theatrical illusion critically within those same forms. As a result, Calderón's most successful plays show an understanding of human nature that incorporates but ultimately surpasses the rigid conception of man in terms of fixed essences. To be sure, there are strong reasons for recognizing this facet of Calderón's work: on the one hand, Calderón inherited peculiarly Spanish values from the earlier epic and comedia traditions which celebrated heroic integrity (entereza) and unvacillating identity (e.g. in the formulaic phrase, “soy quien soy”); on the other, Calderón's language and thought show a distinctively Scholastic bent, a thorough assimilation of the idea of Being as that which is determined as singular and as true (“omne ens verum est” would be the Scholastic slogan). But we have seen that Calderón's theatre, like the earlier Humanist model to which it is indebted for its central, selfconscious conceit of the theatrum mundi, incorporates a vision of man in which human nature is seen in situational terms and in which essences are redefined along the more rhetorical lines of use (meaning “custom,” rather than “utility”) and convention; these refer to the products of human culture – and theatre foremost among them for Calderón – as significant orderings of nature.