Book excerpt: In the teeth of climate emergency, hope has to remain possible, because life insists on it. But hope also has to be realistic. And doesn’t realism about our plight point towards despair? Don’t the timid politicians, the failed summits and the locked-in consumerism all just mean that we have left things far too late to avoid catastrophe? There is a deeper realism of transformation which can keep life powerful within us. It comes at the price of accepting that our condition is tragic. That, in turn, calls for a harsher, more revolutionary approach to the demands of the emergency than most activists have yet been prepared to adopt. This is a book to think with, to argue and disagree with – and to hope with.