This paper was first written some twenty years ago when existentialism was the main sort of anti-analytic philosophy. I wished in this paper to say that existentialism could and should be understood. I did not mean to deny that existentialism was, in some part, nonsense, but I wished to say only that it was philosophical nonsense and that it could be philosophically understood, in the same way that we can understand, for instance, Frege's doctrine that the concept horse is not a concept. What Frege is saying is palpable nonsense, but we can understand why he is saying it.