American Buddhist Net

http://www.buddhanet.net/pdf_file/upanisa_sutta.pdf
http://www.accesstoinsight.org/lib/authors/bodhi/wheel277.html

Tucked away in the Samyutta Nikaya among the "connected sayings on causality" (Nidanasamyutta) is a short formalized text entitled the Upanisa Sutta, the "Discourse on Supporting Conditions." Though at first glance hardly conspicuous among the many interesting suttas in this collection, this little discourse turns out upon repeated examination to be of tremendous doctrinal importance. Its great significance derives from the striking juxtaposition it makes of two applications of "dependent arising" (paticcasamuppada), the principle of conditionality which lies at the heart of the Buddha's doctrine. The first application is the usual one, setting forth the causal sequence responsible for the origination of samsaric suffering. Apart from a slight change it is identical with the twelve-factored formulation recurring throughout the Pali canon. The change — the substitution of "suffering" for "aging-and-death" as the last member of the series — becomes the lead for the second application of dependent arising. This application, occurring only sporadically in the Pali canon, allows the same principle of conditionality to structure the path leading to deliverance from suffering.