Ecosystem management is a magnet for controversy, in part because some of its formulations rest on questionable assertions that are radically contested. These assertions are important to understanding much of the conflict surrounding ecosystem management and, therefore, deserve thoughtful discussion and vigorous debate. Unfortunately, the assertions usually receive little scrutiny because critics, supporters, and the public are, understandably, absorbed in the personal and societal consequences of implementing controversial public policy choices under the rubric of ecosystem management. Professional natural resource managers, typically operating from within government bureaucracies and professional organizations, tend to blunt debate over the critical assertions by depicting ecosystem management as an evolution of past management approaches. Others, usually from outside the traditional natural resource management professions, contend that ecosystem management is revolutionary, not evolutionary. In this more radical view, ecosystem management is much more than a mere reformulation of classic natural resource management. To accept such a radical view of ecosystem management, I propose that there are four necessary, but implicit assertions. None of the assertions is accepted without challenge: each has articulate supporters and detractors. My conclusion from evaluating the radically contested assertions and policy corollaries is that much, but not all, of what is alleged as a scientific basis for ecosystem management is an assertion of fundamental values or, at the very least, an expression of personal policy preferences.