how do we define concept blending?
See http://wiki.opencog.org/w/OpenCogPrime:PropositionsAboutOpenCogPrime#The_Value_of_Conceptual_Blending An a universe of sets where intensional similarity and extensional similarity are well-correlated, if two sets A and B are often useful in proving theorems of the form "C is a (probabilistic) subset of D", then "blends" of A and B will often be useful for proving such theorems as well.
This is a justification of conceptual blending for concept formation
Concept formation: implementation of heuristics for the formation of novel concepts, based on combining prior concepts and on recognizing patterns in the current network of knowledge. Includes basic conceptual blending