Very few of us can make as much sense at any age as Mary Midgley continues to do in her 90s. The philosopher has just published a characteristically trenchant book on the interesting question of whether we actually exist, which takes aim directly at the fashionable supposition that our personalities, and subjectivity itself, are illusions, "in fact no more than the behaviour of a vast assembly of nerve cells and their associated molecules" as Francis Crick put it. But Crick, though a scientist of genius, was not much of a philosopher. That we have selves and subjectivities cannot be a delusion, since there must be something, or someone, to be deluded. Midgley describes philosophy as "plumbing". Over the last 40 years she has flushed a great deal of waste matter away to the general benefit of society, whether this is the windy metaphysics of some sociobiologists or the confusion of science with mythology. Long may she continue.