We turn now, in the phrase of a satirical BBC TV series, to something completely different. If you were to read Bertrand Russell’s still-popular History of Western Philosophy, written before the Second World War, you will find no mention of the branch of philosophy known as existentialism. This is because while, as we shall see, it had its exponents in the nineteenth century, it came to the fore in mainland Europe only in the 1940s, and later still in the English-speaking world. In this chapter we shall look at the ideas of people whose lives overlapped ours (Sartre died as recently as 1980, and I have personally met – at a respectful distance in most cases – several of the others who will be mentioned.) This is therefore a philosophy of our own era, though that criterion is not in itself sufficient to place it higher than earlier schools of thought in any philosophical league table, as one might in the sphere of science.