A couple of things that really rang bells for me recently were podcasts on The Permaculture Podcast and a video, links below. The Lean Logic episode, which then led me to the Transition Towns episode with Rob Hopkins...
Ethics, Domains, and Principles are each on separate layers so can be printed out and then rotated individually and used as a teaching tool / for exploration by students to match different Principles, to different combinations of Ethics & Domains, and think of applications of these combinations.
So, Permaculture Ethic 2 ‘Care For People’, is for one thing, putting humans smack bang in the middle of the design process. So many towns & cities are designed for vehicles: how to get as many vehicles to their destination as quickly as possible, seems to be the main criteria for so much of what we have planned & implemented at a civic level over the last half a century or more.
Care for the Earth. The Earth is our home, with finite resources and a still-growing population. This ethic states something that is very obvious, that we should take care of where we live, but which is so often overlooked or neglected.