I was keen to dispel a familiar misunderstanding: that existentialists somehow relish the alienation of human beings from the world. This may have been Camus's attitude, but it was certainly not that of Heidegger, Sartre and Merleau-Ponty, each of whom tried to show that we can only experience the world in relation to our own projects and purposes. The world is initially one of 'equipment', said Heidegger: it is a world of 'tasks', said Sartre.

The dis-incumbenced stance is the one people should cultivate, we are told, once they recognize that there is no world beyond the human world. They will, indeed must, have their beliefs and values, but they will recognize that these 'lean upon' - and are answerable to - nothing other than human commitments and purposes. The only fidelity, Rorty remarked, can be to our own conventions.

Like Nietzsche, Heidegger also gave up on the prospect that schools and universities would nurture the kind of reflective openness to the way of things that, certainly by the 1940s, he identified with authentic thinking. The authentic person is not the Promethean, iron-willed figure that pops up in Nietzsche, but someone more like the Daoist sages whom Heidegger admired.

It's one thing to assent to propositions like 'The way of things is ineffable', and quite another to internalise what it is being gestured at by such propositions, to get a sense or feel for mystery. For me, at least, it is in and through ways of engaging with nature that this sense is intimated. These ways include being in the garden.

I rather shared Nietzsche's conception of the kind of individual that an ideal education should be cultivating. 'Authenticity' is not Nietzsche's term, but as used by some existentialists, it nicely captures what Nietzsche admired - the resolve of an individual person to forge his or her own 'table of values', to be emancipated from strait-jacketing conventions, traditions, and ideologies. As embodied in the 'Overman', authenticity is the antidote to 'bad' nihilism.

The aim of dis-incumbence is a hubristic one, for it requires confidence in the ability of men and women to live in the belief that nothing they do can, in the end, be justified by anything. That's a belief that it is easy to proclaim in seminar rooms or pubs, but not one that people could actually live with.

The garden is as good a symbol as you can find of a dialectic between spheres of experience - of culture and nature - that presuppose one another.