In the last decades of the twentieth century, there has been more and more interest in research related to metaphor and other phenomena involving conceptual projection. The blending theory approach to metaphor, as devised by Fauconnier and Turner (1994, 1996), has refined the standard two-domain model developed by such cognitive linguists as Lakoff and Johnson (1980, 1999) by introducing other additional input spaces from which information is recruited for interpretation, including a blended space which may develop its own idiosyncratic structure through the mediation of a generic space. Ruiz de Mendoza (1998) has reexamined the standard notion of blending in a critical way. We contend that, in fact, Fauconnier and Turner (1994, 1996) and Ruiz de Mendoza's (1998) accounts are not fully incompatible. Both of them argue for some kind of additional structure in the blended space. The only difference between these two proposals is that while Fauconnier and Turner hold that it is the blended space that creates its own emergent structure, Ruiz de Mendoza thinks that this additional structure is provided by increasing the number of inputs which lend their structure to the blend. We examine a series of examples in order to prove that these mental spaces are invoked by a well-defined context or sheer convention. (Sandra Peña Cervel and Francisco Santibáñez)