People’s reason for wanting a definition is to take care of the borderline case, and this is what a definition, as if by definition, will not do. That is, if an individual asks for a definition of poetry, it will most certainly not be the case that he has never seen one of the objects called poems that are said to embody poetry; on the contrary, he is already tolerably certain what poetry in the main is, and his reason for wanting a definition is either that his certainty has been challenged by someone else or that he wants to take care of a possible or seeming exception to it: hence the perennial squabble about distinguishing poetry from prose, which is rather like distinguishing rain from snow—everyone is reasonably capable of doing so, and yet there are some weathers that are either-neither.
