Permaculture is a system of agricultural and social design principles centered around simulating or directly utilizing the patterns and features observed in natural ecosystems. The term permaculture (as a systematic method) was first coined by Australians David Holmgren, then a graduate student, and his professor, Bill Mollison, in 1978. The word permaculture originally referred to "permanent agriculture", but was expanded to stand also for "permanent culture", as it was understood that social aspects were integral to a truly sustainable system as inspired by Masanobu Fukuoka’s natural farming philosophy.