Sustainability means different things to different people, as you found out on your first homework.

Some, including Professor Schnoor, have called sustainabiltiy a meta-discipline, something that informs and provides the foundation for reserach and knowledge in a number of different areas. David Orr, in his book Earth in Mind, said that ecological literacy should be the foundation for a 21st century eduaction. The World Council on Sustainable Development provides a more specific plan on how to create a sustainable society.