Maybe not just rejecting legal frameworks, but rejecting rational thought (frontal lobes/superego/higher order thought/whatever-you-want-to-call-it) as the most valid way of understanding the multiverse. A person who lives by instinct and feel.
My reading of the alignments may be biased by my attempts at psychological and political realism. Each of the core alignments seems quite closely to approximate a standard position in either political or ethical philosophy; at least enough so for my purposes. And my reading of CN is probably biased by too-long study of libertarian thought.
I guess that I just don't see the need for a fundamental 'alignment' that suggests one has dispensed with rationality as such. Thinking of that sort seems far more a matter of personal makeup (whether psychological or neurological or what-have-you), and it veers too closely to what we could politely refer to as a mild
dysfunction...
A chaotic temperament would definitely be based more on instinct and feel, as you say, but does that imply the absence of reason? I certainly do not think that the rejection of hierarchy is unreasonable...
... It's not just the cosmic mythology that could use a little more science, IMO (still curious about what structure you gave the multiverse if you eliminated alignment-planes) but the Planescape factions and all that logically follows from them. I've been itching to rewrite the Xaositects and Ciphers for a while, or all of them for that matter. They don't make sense...
I'd be curious to see what you come up with; it's been a long time since I've read through the Planescape stuff, but I remember a lot of great starting material. As for my cosmology, it would take a good long while to really detail it, but I'll post some outlines of it soon. I've spent a lot of time talking about it this past week, but I can't get to writing it until I get a few more things done first (I have to detail some races that folks want to play, and I need more sharable information on the country they just entered).
Oh, this seems like rather a different question! For myself, I always saw it more in terms of a higher 'birth-rate' (or whatever). The Baatezu are clever strategists, whereas the Tanar'ri rely on sheer numbers.
Which leads me to wonder why the Baazetu wouldn't have figured that out and started breeding/recruitment programs to catch up. For it to hold, there must be some huge environmental factor in the structure of Baatar that prevents numbers. Look at Earth - the more organized military force, given equal numbers and terrain, almost always prevails over the undisciplined one.
Over the overtly undisciplined, sure, but not necessarily over the more organised; informal guerrilla armies have notched up an impressive track record. But for the Baatezu, I suspect we can look to our own history for analogies. The population of Europe is in decline, and the non-immigrant part of the US is as well. It seems that the more settled and stable the society, and the more advanced the economy, the less inclination there is for breeding (and, conversely, the more incentive there is for having fun and thinking about yourself). Even if you got over the ethical nastiness of eugenics, something the Baatezu would not worry over, there is still the question of desire. If your culture is geared more towards material prosperity and personal advancement, what reason would you have for wanting 13 kids?!