This lecture is a plea for a philosophical standpoint and an ontological approach to Architectural Conservation. Monuments should be considered not as inert remnants of the past to be restored, but as cultural agents to be reactivated. We conserve monuments not for what they have been, but for what they are and the modes in which they can contribute to contemporary cultural life. Towards this end, key concepts in heritage charters and conservation practices, such as heritage values, authenticity, and cultural significance in the documentation, assessment and interpretation of monuments, as well as in various kinds and modes of intervention, are being reconsidered in a new light.