The word biophilia means being drawn to Nature, attracted to the wild places of the world when we are anxious or depressed: a quiet walk over the chalk downs by the Sussex coast of England, a bluebell wood in Somerset, the beauty of the Bay of Naples, seen from Sorrento, a white sand beach in Islamorada, Florida, with its sandpipers and pelikans.

The countryside has an attraction that harks back to the days of ancient mankind, to the semi-wooded savannah of Africa and the unspoiled lands our forefathers trecked across so long ago. They calm the anxiety and bring a sense of peace. Other scenery, like dense woods or, till quite recently, forbidding mountains and deserts, do the opposite for many people and for obvious reasons. We cheer ourselves up instead with miniature gardens or plant pots in our cities devoid of nature.

It is no accident that Epicurus philosophised a garden.