Recent literature has shown an increasing interest in issues pertaining to the theme of ‘parts and wholes’ in Plato. One classic example is Verity Harte’s 2002 monograph Plato on Parts and Wholes: The Metaphysics of Structure (OUP), which revisits the mereological question of what constitutes a ‘whole’ in the philosophy of Plato. The main achievement of Harte’s investigation rests in the notion that structure is ‘irreducible’ to the characterisation of a whole. To be a whole, therefore, is already a normatively value laden concept in Plato, insofar as it presupposes an ordered structure or arrangement of internal parts.

Many of Plato’s works are strongly preoccupied with complex wholes. Unlike the objects of the intelligible realm, however, Plato assumes that complex items are prone to internal conflict and stand in need of proper direction. Importantly, complex wholes are able to function better as the kind of entity they ought to be when they acquire their own unique structure and order. Given this normative requirement, Plato is left with the task of explaining exactly how complex wholes are optimally ordered or structured so as to become whole. Whilst recent literature has focused mainly on the ‘mereological question’ in Plato, these aspects of Plato’s engagement with the theme of parts and wholes seem to have gone underappreciated.

This thesis aims to fill that gap by exploring the different models Plato puts to work in different dialogues for conceptualising the well-orderedness of complex wholes, with special focus on the city, the soul, and the cosmos. By critically examining Plato’s presentation of these structures in dialogues placed within a chronological framework, this thesis asks whether Plato’s account of ‘well-ordered wholes’ improves over time. This question will be examined with particular attention to the psychological, ethical, and political implications of the different conceptual models of structure Plato offers across the dialogues. In the light of these questions, this thesis will propose that Plato’s later dialogues contain his most successful account of well-ordered wholes by promulgating a holistic conceptual model which offers a more integrated and less hierarchical account of the well-orderedness and unity of complex wholes.