It has been noted that the use or non-use of synthetic chemicals is not a particu-
larly rigorous scienti®c basis on which to determine a system's sustainability, how-
ever this dichotomy has been used in the discussion because of the prohibition of
synthetic chemical inputs in organic farming. Rather than attempting to categorise
certain farming methods as sustainable, which would contradict the view of sus-
tainability expressed above, some issues that merit attention have been highlighted.
The extent to which any farming system which is intended to be sustainable
should be linked to an unsustainable society is one such issue. These links may take
the form of purchased inputs, including energy, or the sale of farm output. Clearly
no farming system can entirely seal itself o from the rest of the planet, but there are
important questions as to whether sustainable farming systems should aspire to as
great a degree of self-suciency and self reliance as possible and at what level should
sustainability assessments be made.