Dialogue has emerged over three decades as a distinct field with multiple threads: collective social intervention, deliberative democracy, diplomacy, organisational development. Yet despite this growth, there are no shared standards for excellence or ethical performance; no unifying ideas about the knowledge underlying these efforts. William Isaacs, whose work with David Bohm helped establish the field, addresses what's needed to professionalise dialogue. Drawing on Donald Schön's critique of technical rationality, he argues that professional knowledge must include tacit embodied knowing, a theory of 'the thing' being addressed (in dialogue, this is incoherent thought), and understanding of micro-patterns of behaviour. The theory of change centres on 'containers'; holding environments that evolve through phases: politeness, disturbance, inquiry, and flow. Isaacs concludes that what's missing is explicit recognition of the Self; individual and collective; as the source of subtle intelligence that can transform fragmented thought and identity. This paper provides essential theoretical grounding for the Academy's professionalisation efforts.