I've definitely learned a few things here (btw, NW, re. "being good without ethics", I've heard some talk about "following your heart" and "intuition" but I didn't quite get it for the reason you point out -- it just seems like the choices are A] seek to understand the heart's reasons or B] hope to goodness your heart is smarter than your head), but I'm with Oli; on-the-spot judgements that deliberately avoid exact definitions are probably the best use of this concept in the first place. Do it for fun rather than science. Or even !!fun!! rather than science. Heck, even do it for !!science!! rather than science.
Everyone has their own internal way of viewing their place in the world, and how their actions define themselves. Through that, one's behavioral code develops.
You can call it "just intuition" or something like that, but then, you're basically declaring the difference between being lawful and being chaotic the difference between whether you are capable of enough self-reflection to merely recognize and state out loud what you consider right and wrong.
Much like defining "Lawful" as merely not having committed a crime, this is taking a far too literal approach to the fundamental conflicting viewpoints people take in life.
Even lawful people, after all, are doing what they think is right based upon their own emotional weighing of the issues.
Consider, for a moment, that in the Egyptian afterlife, you were judged not based upon whether you lead a virtuous life or not, but your heart was weighed against a feather of Ma'at - the god of society. You were judged based upon your
peers, not upon your morality as for whether you would be allowed to exist in the afterlife, or have your soul fed to the great devourer.
If you were out of step with society, even by being
too virtuous, you were considered a terrible person, worthy of ultimate destruction.
The difference between the lawful and the chaotic personal ethical code is that a lawful person is keenly aware of the social mores and customs, and builds their ethical code in part out of peer pressure and conformity to the norms of the society around them. They bristle when they move into or experience new cultures that challenge them by changing what the norms are.
Chaotic ethical codes, by contrast, either do not care or openly delight in being flagrantly in opposition to society's norms, and they tend to enjoy "sampling" different cultures.
The difference is in whether one fundamentally sees being part of or standing out from to the crowd as a core element of their personal identity. Fulfilling that identity they have chosen for themselves is the place from which that ethical code springs.