In fourth-century Greece (BCE), the debate over the nature of philosophy generated a novel claim: that the highest form of wisdom is theoria, the rational 'vision' of metaphysical truths (the 'spectator theory of knowledge'). This book offers an original analysis of the construction of 'theoretical' philosophy in fourth-century Greece. In the effort to conceptualise and legitimise theoretical philosophy, the philosophers turned to a venerable cultural practice: theoria (state pilgrimage). In this practice, an individual journeyed abroad as an official witness of sacralized spectacles. This book examines the philosophic appropriation and transformation of theoria, and analyses the competing conceptions of theoretical wisdom in fourth-century philosophy. By tracing the link between traditional and philosophic theoria, this book locates the creation of theoretical philosophy in its historical context, analysing theoria as a cultural and an intellectual practice. It develops a new, interdisciplinary approach, drawing on philosophy, history and literary studies.