Scan almost any forum on almost any topic and you'll come across discussions of the kind we've been having in this forum. Beer-drinking mammals have great difficulty categorizing and defining vague but important concepts. Try defining the concept 'game' for example. On the one hand, we find it useful to impose or create an intelligible structure under which we can place diverse cases. On the other, we impose upon ourselves the ridiculous goal of trying to define our concepts by giving necessary and sufficient conditions to trace the 'common denominator' across cases. This is, in most instances, impossible (again, think of the example of the concept of a 'game'). Concepts of this sort do not share common characteristics across all cases. They merely share family resemblances. And that is enough.
The moral? I think TBN is on the right track: brew beer, not styles.
Ps. can you tell I used to study philosophy? <!-- s:lol: --><img src="{SMILIES_PATH}/icon_lol.gif" alt="

" title="Laughing" /><!-- s:lol: -->