The discipline of Enterprise Architecture (EA) is still relatively immature and incoherent. The discourse is rather fragmented and lacking a shared vocabulary. To shed some light on the situation, some schools of thought on EA have been suggested, each with its distinct concerns and set of assumptions. In this article, we aim to bring more structure and clarity to EA discourse. Not only do we review the identified types and schools of EA, but we also attempt to make sense of the underlying structural and metaphysical underpinnings of the field and to ground EA in theory. As per our analysis, requisite architecture methods and tools are contingent on the level of complexity. In particular, while best practices and linear techniques are applicable in a contained operational scope, they fall severely short in addressing complex problems pertaining to non-linear discontinuities inherent in the increasingly interconnected and global business environment. On the other hand, we view that an ideal scope of an architecture “work system” is bounded by a maximum number of people able to create a shared meaning. Accordingly, we propose that architectural work in an enterprise be divided into three distinct yet interlinked architectures: Technical, Socio-Technical, and Ecosystemic. Each of these architectures is selfregulated, based on different ontological and epistemological assumptions, has its own vertical scope, and requires its own distinct methods and tools.