True neutral characters sometimes find themselves forced into rather peculiar alliances. To a great extent, they are compelled to side with the underdog in any given situation, sometimes even changing sides as the previous loser becomes the winner. A true neutral druid might join the local barony to put down a tribe of evil gnolls, only to drop out or switch sides when the gnolls were brought to the brink of destruction. He would seek to prevent either side from becoming too powerful. Clearly, there are very few true neutral characters in the world...
- 2e Player's Handbook
...And clearly this is ridiculous.
Let me start off by saying I don't see something inherently ridiculous in the idea of there being certain entities who would wish for the universe to exist in balance between good, evil, law and chaos. It's an old, old idea - indeed one of the oldest ideas of fantasy literature - and it has a certain rationality: too much good and too much law can be bad things. (Just as the extremes of the political left and the political right loop round and bleed together at the boundary, we can envisage the purest good resulting in just as much wrong as the worst evil, even if the root motivations are different.)
There is, however, something ridiculous in the idea of a single druid suddenly switching sides in a given conflict in order to perpetuate it indefinitely - "It's okay, Mr. Gnoll. I'm with your lot now, honest. Well, at least until you regain your strength...then I'm back with the Baron." It's a classic case of confusion of the microcosmic with the macrocosmic: a little like a government basing its climate change policy on the sunny weather today, and then, when it rains tomorrow, drafting a new bill altogether.
No, surely if True Neutral characters in the classical sense are to work at all, they have to take a long term view of general trends. It isn't about maintaining the balance of power between some minor aristocrat and a gang of gnoll bandits. It's about judging the sweep of history and acting at crucial moments to try to influence the broad progression of events. True Neutral characters in this sense are a bit like Benjamin Disraeli, pursuing a policy of Splendid Isolation; stay aloof from the affairs of the world, unless it seems that Prussia is gaining the upper hand against France - and then, if possible, strike to maintain the balance.
This sort of character could be extremely enjoyable to play, and a whole campaign could be centred around the concept, but it would have to be a one-alignment affair, with the entire party working in concert - because otherwise what reason would non-True Neutral characters have to cooperate? And the set-up would require a campaign world of such political detail that most DM's would balk at the prospect. Worst of all, the temptation to set up a story arc and firm railroads would be too much for even the staunchest of us to resist.
Much easier and more sensible to conceptualise True Neutrality as Apathy, I feel. Although now that I think about it, I don't much care either way.