In 1859 Herbert Spencer recognised that the key curriculum issue was not what to include but what to leave out. What to leave out marked a shift in curriculum discourse from a search for universal approaches and absolute principles towards curriculum questions understood as only resolvable relative to particular social contexts. Yet outdoor education is frequently explained and justified in universal, absolute terms that are incapable of resolving the question of outdoor education's educational worth in any particular situation. The first part of this study outlines some necessary links between curriculum discourse and outdoor education theory. The second uses outdoor education textbooks to investigate how context-free rationales for outdoor education have been framed. It found textbooks used one or more rhetorical devices: (1) treating education as personal development, with only limited acknowledgment of the social functions and contexts of education, (2) omitting the outdoors from aims and purposes, or treating the outdoors as monolithic, and (3) describing aims and purposes in broad and abstract terms. Adopting any or all of these positions drastically reduced the capacities of the proffered theories to (a) help determine if any given program was necessary or (b) help determine what programs were necessary. The article concludes that the evident flaws in textbooks indicate a more widespread failure in the outdoor education literature to comprehend curriculum questions.