Cognitive Linguistics 14–1 (2003), 91–96 0936–5907/03/0014–0091 © Walter de Gruyter Squib Mental spaces: Exactly when do we need them? PETER HARDER Since the first publication of Fauconnier’s Mental Spaces in 1985 there has been a growing field of applications of the central concept that is indicated in the title. A recent elaboration of the mental spaces approach is the exploration of processes of conceptual integration, in which the simultaneous invocation of two mental spaces brings about a third. Blending spaces gives fascinating results, because previously disparate properties can be brought to co-exist in the same mental space with pro- perties that were found in neither of the original spaces. An example is land yacht (cf., e.g., Fauconnier 1998: 271), where the “sailing space” and the “driving space” are integrated to produce a mental space where the driver of a conspicuous car is cast in the role of yacht owner. This example simultaneously illustrates how the concept can be brought to bear on grammatical phenomena such as compounding, since the two spaces are blended as part of the process of forming the new compound noun. More generally, Eve Sweetser (1999) has demonstrated how mental- space blending can be brought to bear on the issue of compositionality. Because of mental spaces, the usual objections against compositionality in cases such as fake gun (that it cannot simultaneously be a gun and a fake) can be handled: the object is a gun in one mental space but a fake in another. The theory is attractive, since unless it is a gun in one space, it cannot be called a fake in another; a pencil is not a gun, but that does not qualify it to be called a fake gun. In a similar vein, Fauconnier and Turner (cf., eg., 2002: 370) have argued that blending is a central process of grammar. They illustrate the claim with the “caused motion” construction (cf. Goldberg 1995), demonstrating that the insertion of a verb like sneeze (which does not in itself designate caused motion) can be understood as working by virtue of a blending process. Thus, when we interpret He sneezed the napkin off the table, we integrate a space containing an unintegrated sequence of events (including the event of sneezing) with a space containing the integrated caused-motion schema associated with the construction as exemplified in prototypical cases like Jack threw the ball