In this article it is shown that, taking into account the main ideas of Sorace’s (2000, 2004) descriptive works on auxilary selection, you can explain in a natural way some of Batlle’s (2002) main contributions in connection to Old Catalan. Therefore, for instance, it is expectable that stative and action verbs are the first kind of verbs to admit the substitution of the auxiliary ésser through haver, because these verbs are located in an intermediate position in the so-called Auxiliary Selection Hierarchy. It is also shown that the limits between the lexical semantic classes involved in auxiliary selection are established in a gradual way. Finally, we outline that some of the basic problems descriptive perspectives have in connection to auxiliary selection can be solved by explaining and justifying which are the semantic correlational features that can be codified in the syntax of the argumentative structure in a transparent way (Mateu 2002).