This thesis uses an ethnographic study to explore the cultural logic that shapes the livelihoods of the Nɨpóde-Uitoto people who live along the middle reaches of the Caquetá river in lowland Colombia in Northwest Amazonia. The perspective of the study is a culturalist one, which seeks to understand the Native Amazonian economy from the point of view of the Nɨpóde-Uitoto themselves. Ethnographic material on subsistence, ritual and commercial activities is presented to demonstrate that Uitoto mental representations and metaphysical concepts of the cosmos not only inform but actually shape and direct their material processes of livelihood. The study also shows that swidden cultivation forms the core of the indigenous economy, and that this gardening livelihood is embraced by the Nɨpóde-Uitoto as a religious and moral way of life. By examining a series of formal oral texts about horticulture, the discussion reveals that the Uitoto hold a dualistic cosmology, in which life is seen as a ceaseless struggle to repel de-humanising and pathogenic forces in the cosmos. It is argued that the Uitoto see their gardening activities as a continuous affirmation of their humanity, and as the practice of cleansing internal human space through the expulsion of harmful elements to the "outside": the peripheral space beyond the house and settlement. Within this schema of concentric dualism, subsistence activities are conceived of as a continual process of selecting useful elements from the "outside" which are then purified into life-giving substances for incorporation into the physical body and social corpus on the "inside". As well as fostering social peace within the human community, garden work strives to maintain cordial relations with parental divinities and related garden plant spirits, who sustain and protect humanity from negative forces in the cosmos. In the same way, regular labour effort in narcotics processing, and the production of garden surpluses forceremonial exchange, has as its fundamental logic the strengthening of the support of divinities and ancestors who ensure continued social reproduction. Overall, Uitoto models of livelihood feature a pervasive logic of reciprocal nurture, care and helping between humans, and between humans and spiritual beings. Alongside the key cultural rationale of reciprocity, Uitoto theories of work and well-being focus on cyclical bodily processes. The primacy of a bodily idiom reveals cultural models of a "corporeal economy" and a "healing economy", which may find correlates in Amerindian models of livelihood and social reproduction throughout the ethnographic region. Examination of native perspectives on commerce shows that the Uitoto construct a dualistic model of their mixed livelihood which they use to organise their work strategies in the short and long-term. As well as a secure source of food, native people value subsistence gardening as a specific practice which not only expresses, but also guarantees their Amerindian personhood: for the Uitoto, their livelihood practice is an essential part of ethnic identity.