This article reveals the ways in which concepts associated with the humanities inform determinations of ‘outstanding universal’ aesthetic value of natural heritage under the World Heritage Convention. Language derived from humanistic ideas of beauty, the sublime and the picturesque, together with a range of images, are used in World Heritage deliberations to describe nature from, in the words of the treaty, ‘an aesthetic point of view’. However, a preference for ‘scientific method’ masks the use of humanistic approaches, impeding the development of critical approaches that could enhance World Heritage determinations. The deliberate use of humanistic methods and images to judge environmental aesthetics would, the article contends, facilitate critical inquiry without falling foul the ‘principle of legality’ – an international legal requirement of international bodies such as the World Heritage Committee to act in accordance with the powers conferred on them by the states parties under a treaty.