Although the loss of certainty in the age of postmodernism is questioning knowledge production in general, the emerging discourse of lifelong learning demands a different theory of adult learning in particular. This article aims to offer a conceptual tool for describing learning in adulthood in terms of postmodern and lifelong learning conditions. It approaches the problem from the images of learning and learner that adult education scholarship has produced and identifies that adult learning theory attempts to signify foundational certainty by using binary-trapped adjectives. The author argues that insofar as we continue with the adjective-plus-learning theory, we cannot escape binary thought. The author proposes a new concept, rhizoactivity, to navigate multiplicity of learning in a postmodern world. Anticipated benefits of employing rhizoactivity in understanding learning are discussed in terms of postmodern and lifelong learning conditions.