The thesis aims to present Leibniz's monadic system as the simplest conceivable structure. To this end, the thesis employs both contemporary literature concerned with formal ontology and its logic, semantics and the nature of reference; and Leibniz's own writings coupled with correspondent commentaries, including articles transcending selected interpretive issues into present-day discussions on actualised versions of one of the essential Leibnizian principles: the identity of indiscernibles. The exposition proceeds in three steps: (i) developing concepts of structure, determination and reference in critical confrontation with contemporary approaches, then (ii) applying those concepts to the interpretation of Leibniz's principle of identity of indiscenibles and illuminating therewith links between ontology and semantics, and eventually (iii) utilizing those findings in clarifying the mirroring relation constitutive of the monadic structure as represented a) in Leibniz's own spatiotemporal illustrations and b) in formal models in secondary literature. Acknowledging that the simplest conceivable structure, which is the monadic structure, can neither be satisfactorily expressed by spatiotemporal illustrations, nor can it be represented in formal system, itself forming the limit of extrinsic...