At a conference on the topic in Ohio in 1988, Bob Rodale
said: It is a question. He was quoted several times on that
definition during the remainder of the conference! Check on the
book *Sustainable Agricultural Systems*, edited by Clive Edwards,
Patrick Madden and others. Rodale's presentation is one of many
chapters - (and I found the quote: ". . . sustainability is not
basically a method; rather it is a question about permanence.")
The book was available from SWCS, 7515 N.E. Ankeny Road,
Ankeny, IA 50021-9764 for $40. Hardcover, 696 pages.