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.

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 think it's true that for existentialist thinkers, appreciation of what we are - free, makers of meaning, 'issues' for ourselves, and so on - is at the same time a recognition of how we should try to live.

In all great civilizations, garden discourses have belonged to larger discourses about beauty, the good life, the relation of humankind to nature, and so on.

The writing I have in mind and sometimes indulge in myself is concerned, not with plants, mountains or birds as items of scientific description, but with experiences of nature that impinge upon our moods and emotions, enrich our imagination and reveries, and shape our sense of how we stand in relation to the environing world. In a broad sense of the term, this kind of writing is an exercise in phenomenology, an attempt to render the significance that birds, plants or whatever have for us.

What impressed me about Plato and Sartre was their conviction that we should live our lives in the light of big truths about reality and human existence.

My 'heroes' are those - like Chuang Tzu and Heidegger - who recognize that the world of experience is a human world, but recognize too that there is a 'way' or a 'source' to which our lives are answerable.