This chapter proposes how indigenous knowledge develops holistic approaches. It discusses the rules-of-thumb that cut across complexity. Some of these rules produce indicators that can be used in environmental monitoring. The chapter explores on practices that seem to show complex systems thinking. It describes a theory of indigenous knowledge and complexity. The chapter focuses on the knowledge and practice of Caribbean fishers of Grenada, treats local knowledge as a fuzzy logic expert system. It also focuses on Inuit observations of Arctic ecosystem contamination, provides a fuzzy logic analysis of indigenous knowledge. The accumulation of evidence, especially since the 1990s, indicates that some indigenous groups have resource-use practices that suggest a sophisticated understanding of ecological relationships and dynamics. Many examples seem to show an understanding of the key relationships on the land as a whole, that is, a holistic as opposed to a reductionistic view.