That's one dimension, James. Physics are important.A. If you peg morality in your mechanics to a 2d bar, your moral choices will be 2 dimensional. No writer can write around this, no level of voice acting is going to save you.
but,
An invisible system is better, too.I actually prefer a three-dimensional axis.
Law - Chaos
Good - Evil
Pomposity (or self-righteousness) - Modesty
With neutrality in the middle, of course
Many RPGs would do better by hiding the framework (RPG in a general sense, anything that involves roleplaying elements).