Among the operas on which Mozart and Da Ponte collaborated, Così fan tutte is a special case. In some ways, the libretto is more conventional than those provided for Le nozze di Figaro or Don Giovanni, and Mozart was not the first composer asked to set it. To understand the work best, it is necessary to read the text closely. This article concentrates on a few, highly significant characteristics – in particular, the locations in which the opera takes place. Such details provide the foundations for surprising insights into the opera. First, the libretto deals with central issues in eighteenth-century aesthetics, but the mechanist philosophy that informs the plot (reminiscent of that theorized by Julien Offray de La Mettrie in L'Homme machine) defuses these issues over the course of the action. Secondly, the music that turns the libretto into an opera resonates with specialist issues of eighteenth-century music aesthetics, often to turn them, once again, on their heads. In the last analysis, Così fan tutte is an opera in which both text and music question truth and reliability, and the consequences are serious for the opera, for music and for the very Enlightenment itself.