Guided by an original analysis of the fundamental idea of emergent property, uncovers the distinct significance, but also incompleteness, of the systems approach as a theory of human epistemological engagement. The incompleteness is treated through a non-eclectic interdisciplinary investigation which meets ten distinctly developed criteria required of any potential interdisciplinary partner to systems thinking. There results a theory of knowledge – an epistemology - which is systemic in both senses of the term: it belongs to the general systems movement, and it is systemically structured. The systems movement is thus offered a distinct epistemological voice which can compete on equal ground with other philosophical/epistemological positions. In true systemic fashion, this theory of knowledge also offers methodological, ethical, and existential implications.