The art of rhetoric may be defined as changing other people's minds (opinions, beliefs) without providing them new information. One technique heavily used by rhetoric employs analogies. Using analogies, one may draw the listener's attention to similarities between cases and to re-organize existing information in a way that highlights certain regularities. In this paper we offer two models of analogies, discuss their theoretical equivalence, and show that finding good analogies is a computationally hard problem. © 2013 University of Venice.

Aragones acknowledges financial support by the Generalitat de Catalunya Grant number 2009 SGR 1126, the Spanish Ministry Education and ScienceECO2012-37857 and the Barcelona Graduate School of Economics. Gilboa and Schmeidler acknowledge ISF Grant 396/10 and ERC Grant 269754 (Gilboa). Postlewaite acknowledges support from the NSF

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