Knowledge management systems (KMS) are systems designed to support organizational knowledge processes. Knowledge-oriented theories of the firm are emerging, as theories of KMS design continue to evolve. This paper adopts Habermas'theory of communicative action and discourse ethics [Drake, B, Yuthas, K, and Dillard, J F., 'It's Only Words - Impacts on Information Technology on Moral Dialogue', Journal of Business Ethics 23: 41-59, 2000, Habermas, J., The Theory of Communicative Action: Reason and the Rationalization of Society,' Beacon Press Books, Boston, MA., 1984, Habermas, J., 'Reconciliation through the Public Use of Reason: Remarks on John Rawls's Political Liberalism,' Journal of Philosophy, Vol. 92, No. 3, March, 1995, 1109-131.], and Churchman's [Churchman, C.W., The Design of Inquiring Systems: Basic Concepts of Systems and Organizations, Basic Books, New York, NY, 1971.] Singerian inquiring system as kernel theories [Van Gigch, J.P., 'The Paradigm of the Science of Management: In Celebration of C.W. Churchman's 80th Birthday,' Interfaces, 25 (2), March - April 1995, 81-88.] on which to base KMS design principles. Specifically, we build on Churchman's nine requirements for an object to constitute a system and his Singerian inquiring system, and Habermas' critical theory to develop the notion of Churchmanian-Habermasian knowledge management systems (CHKMS) and principles for their design. We define a CHKMS as a purposeful, ethical and adaptable system that creates exoteric knowledge (relevant for solving social and managerial problems) through communicative action, providing a link between knowledge and action in an organization or community of practice. The design principles involve a strong emphasis on ethical behavior, the development of success measures for CHKMS, the need to ensure that the CHKMS enhances the dignity of humankind, a highly participatory design process, the desire to unify the designers, the decision makers and clients, the need to shape CHKMS components in relation to the system as a whole, and the need for a 'guarantor'to validate knowledge through discursive communication and the 'cashing in' of validity claims. The principles are illustrated by applying them to management of knowledge concerning pediatric bipolar disorder. The implications of the design theory for KMS research are discussed.