Part I discusses what kind of ‘advances’ occur in Hegel's works, particularly his Philosophy of Nature. I then discuss evolution and extinction in relation to these advances. I summarize Errol Harris' view that Hegel's advances are consistent with current evolutionary theory and then critique this view using articles by Cinzia Ferinni and Alison Stone. I discuss an alternative, post-Kantian Hegelianism which dialectically unites the nature of our cognition with us as subjects that cognize (spirit). For that, I draw on Hegel's (...) claim that ‘The True is just as much Substance as Subject’, and I show how that claim is complicated in a helpful way when applied to the multiple kinds of ‘subjects’ in the Philosophy of Nature. Part II highlights the implications of biological mass extinction for these differing Hegelian theories. Part III brings the above post-Kantian dialectical Hegelianism together with the final chapter of the Phenomenology of Spirit in order to align Hegelian terminology with current solutions for mass extinction: ‘Absolute Knowing’ is a self-sacrificing and a recollecting that reinstates the subject in and through nature; such knowing generates dialectically holistic logics of survival. This recollection of life produces neither abstract spiritual self-consciousness nor a mere ‘gallery’ of extinct life forms. It is philosophical responsibility, identity through natural differences, Absolute Spirit ‘tarrying’ with its world. 21st century Hegelians should be environmentalists on Hegel's terms, a surprising conclusion given that Hegel did not anticipate environmental problems. Hegel's Philosophy of Nature may in turn help environmentalists argue against unacknowledged and badly conceived philosophies of nature. Hegel's work is not reducible to either naturalism or metaphysical idealism: reading Hegel's Philosophy of Nature in conjunction with his Phenomenology of Spirit reveals ways in which a subject, widely and complexly defined at different levels (including different species), is dialectically inseparable from substance, equally widely and complexly defined. This helps us to understand the natural depths of Spirit, which we are at risk of losing. (shrink)