The EE organisational essence theory, or ALPHA theory, is a theory about the distinction of layers of transactor roles in an organisation, based on the sort of production that transactors bring about: original, informational, documental or material. Original production comprises all production acts that result in original new facts. Examples are devising things, deciding and judging as well as manufacturing, transporting and observing things. Informational production acts comprise remembering, computing and deriving facts and sharing (remembered or derived) facts. Documental production acts comprise saving, providing and transforming documents or data (containing facts). Material production comprises storing, retrieving, copying, transmitting and destroying files. Accordingly, the organisation of an enterprise can be partitioned into four partial organisations: the O-organisation (O from original), the I-organisation (I from informational), the D-organisation (D from documental) and the M-organisation (M from material). The I-organisation supports the O-organisation by means of informational services (remembering and sharing facts), the D-organisation supports the I-organisation by means of documental services (saving and providing data or documents) and the M-organisation supports the D-organisation by means of material service (storing and retrieving files). Because original acts are the only acts that change the state of the ‘business’ world of an enterprise (i.e. the production world of its O-organisation), they must be performed by human actors. For I-, D- and M-acts, it holds that they can be taken over by artefacts, notably ICT systems, including AI artefacts (like logistic control systems and robots). However, as pointed out in the PSI theory, human actors are ultimately responsible and accountable for the acts of these artefacts. The ontological model of an enterprise’s O-organisation is called its essential model. Like every ontological model, it is abstracted from implementation, but it is also abstracted from realisation, i.e. from the supporting I-, D- and M-organisation. Yet it contains everything that is needed to understand the essence of an enterprise’s operation. The ALPHA theory contributes to the generic enterprise engineering goal of intellectual manageability by an unprecedented reduction of complexity. It also clarifies that every enterprise information system (EIS) is nothing more or less than a part of the I-, the D- and the M-organisation that support the O-organisation, only implemented by using ICT.