The probable and the marvelous are the two pivots... Comedy revolves entirely around the probable and does not at all admit the marvelous. Tragedy blends the marvelous and probable. As dramatic poetry is entirely confined to the probable, is it not necessary that there must be another opposite kind--opera--confined to the marvelous, while tragedy holds the middle between the two, a blend of the marvelous and the probable? You will find proof of this in that whatever makes a comedy beautiful is a fault in an opera, and what charms in an opera would be ludicrous in a comedy.
--Charles Perrault, Paralelle des anciens et des modernes en ce qui regarde la poesie