This paper was originally presented to a research seminar at the Bartlett School of Architecture and Planning, University College London. It formed part of a series of papers relating to a revision of the School’s academic policy which, it was suggested should encompass “a commonly held direction of (development), a unifying theoretical position and (the maintenance of) a secure research base”. The paper is relevant to all of these aspects of academic endeavour in architecture and planning but its actual purpose, to move environmental discourse away from esoteric introversion and towards a wider socialisation of environmental knowledge, is I hope, self-evident. I have left the paper in the first person style in which it was written for delivery at the seminar. There are two assumptions built into this paper. First, that we all accept that what we do implies a social as well as a professional responsibility, or at least that the former is subsumed in the latter, and secondly that we are all concerned to improve the human estate, and that we wish to judge success in the same terms as those who experience it. It is one of the characteristics of the middle and late Twentieth Century that the feedback from society to institutions happens with ever-increasing speed, and thus public judgement of social, cultural or technological success is more rapid, more poignant. I am not suggesting a market research approach to planning and architecture; nor do I have a formula. Let me say only that the vast majority of the recipients of, or participants in, the changes eventually induced by theory. research and development, education and practice in planning and architecture and it applies equally in other disciplines such as medicine understand little of the sophistry of our explanations or justifications. We expect public socio-spatiai judgements somehow to internalise all those matters which form the subjects of our research and education. Of course, they do not do so, and herein lies the issue of common understanding. Herein also are numerous links with current topical issues: the arising debate on democracy in education, so-called ‘grassroots’ professional activities in architecture and planning, the relationships between academic endeavour and the dissemination of knowledge, etc. Let me turn for a moment to a brief description of the problem which confronts any attempt to unify understanding. Developing earlier criticisms of the man-environment paradigm, several years ago Hillier and Leaman (1973) drew a distinction between the logical and the rational il~terpretation of science.