One modern incarnation of the debate between nominalism and realism is to be found in philosophical arguments about sets.  There are two ways of characterizing a set: intensionally, through description (e.g. the set of all inhabitants of London, to use an example of Russell's), and extensionally, which is just a list of the members of the set.

I've been thinking about quotations out of context for a long time: probably since Ray Bradbury made me fall in love with Yeats without my reading a word of him except Bradbury's quotations in title and epigraph. When such quotations are great -- and really that's the most fundamental reason for wanting to quote, or at least for remembering quotations, getting them by heart -- there are two ways they can be great: