part about the potential immortality of protozoa". Ernest Jones considers Freud's claim on Eitingon "a rather curious request ... [perhaps] an inner denial of his novel thoughts about death having been influenced by his depression over losing his daughter". Others have also wondered about "inventing a so-called death instinct — is this not one way of theorising, that is, disposing of — by means of a theory — a feeling of the "demoniac" in life itself ... exacerbated by the unexpected death of Freud's daughter"? — and it is certainly striking that "the term 'death drive' — Todestrieb — entered his correspondence a week after Sophie Halberstadt's death"; so that we may well accept at the very least that the "loss can claim a subsidiary role ... [in]his analytic preoccupation with destructiveness". Continuation of themes in the essay On his final page, Freud acknowledges that his theorising "in turn raises a host of other questions to which we can at present find no answer". Whatever legitimate reservations there may be about "the improbability of our speculations. A queer instinct, indeed, directed to the destruction of its own organic home", Freud's speculative essay has proven remarkably fruitful in stimulating further psychoanalytic research and theorising, both in himself and in his followers; and we may consider it as a prime example of Freud in his role "as a problem finder — one who raises new questions ... called attention to a whole range of human phenomena and processes". Thus for example André Green has suggested that Freud "turned to the biology of micro-organisms ... because he was unable to find the answers to the questions raised by psychoanalytic practice": the fruitfulness of the questions — in the spirit of 'Maurice Blanchot's sentence, "La réponse est le malheur de la question" [The answer is the misfortune of the question]' — remains nonetheless unimpaired. Freud's later writing and legacy The distinction between pleasure principle and death drive led Freud to restructure his model of the psyche. With Beyond the Pleasure Principle, Freud also introduced the question of violence and destructiveness in humans. These themes play an important role in Civilization and Its Discontents, in which Freud suggests that civilization has repeatedly tried and failed to repress the death drives. Freud's indication "that in cases of traumatism there is a 'lack of any preparedness for anxiety' ... is a forerunner of the distinction he would