AimsThe author seeks to show that Freud's text of 1920 is the development of a hypothesis organising a field of experiences that initially appear heterogeneous, and are indeed presented as such by him. The issue is not that of integrating the concept of drive into a biological conception of life and death, nor is it a metaphysic that could unite sexual and biological conceptions. It is the answer to a question: is it possible, in psychoanalytical practice, to evidence a symptomatic or cultural phenomenon in which what relates to the destructiveness of drive can be envisaged independently from the principle of pleasure, as aimed at satisfying the psychic apparatus? This text has been read in rather fragmented manner, whether by psychoanalysts both in favour of and opposed to the notion of the death drive (Winnicott for instance), or by philosophers (Derrida or Deleuze). MethodsThe overall construction of the text and its logic is reappraised to measure the importance of the three passages that are generally singled out and emphasised: the fort-da game in the child, the evolutionist idea that drives, like living cells, have a tendency to head for death, and the reference to Alcibiades’ tirade about love in Plato's Symposium. The Freudian method here is comparable to that of Galileo, who conducted all possible experiments on the grounds of his hypothesis about the time taken for an object to fall: he reasoned on the basis of numerous experiments, showing that none of them enabled the factor that we now call “uniformly accelerated motion” to be demonstrated. It is the difference in misfit of each experiment with the hypothesis that validates that hypothesis. Freud calls in turn on war neuroses, children's games, adults’ pleasure in tragic drama, and negative transfer to show that his hypothesis of a death drive that is independent from the pleasure principle is verified (almost) solely in the pleasure experienced by adults when envisaging a catastrophe for human life. It is not verified in the case of children's games. All the other examples are given to illustrate cases of a mixture of the two principles. It is this negative implication of many experiments, here in the clinical field, that leads him to what he calls his biological speculation. This speculation, given all the different readings and hesitations of the biologists of his time from whom he explicitly distances himself one by one, is an attempt to explain how the drive for destruction arising from transferential repetition is the downside a contingency that is essential for the destructiveness underpinning drives but transposed during the cure (Übertragung), and how it can, in the formation of the unconscious and in particular of dreams, invent new circuits and new objects, the materials for which are found in what is liable to lead to the shorter circuit of death. Biological speculation is never isolated, since Freud then returns to Eros/Thanatos, reading Plato, and then Schopenhaumler to criticise him along with Fliess, who for his part believed in the biological death instinct, in a holistic epistemology. He never leaves the clinical domain, since the text ends on sadism and masochism as clinical phenomena defining the eroticisation of whatever tends towards a radical destruction of self and other. Results1. The hypothesis of the death drive anticipates contemporary work on apoptosis in the two fields (formation of organisms and formation of sexual drive), showing an analogous relationship between the determination of destructive components and the contingency of factors that delay the destruction, while at the same time linking with the destructive factors. The result is that what we call the living in biology is the sexual unconscious in psychoanalysis. The analyst is the instrument creating the conditions for this new articulation to occur. It distinguishes chance in biology from contingency in psychoanalysis. 2. By questioning the psychological distinction between interior and exterior for the psychic apparatus, the Au-delà also enables discussion of the theory of Catherine Malabou in Les Nouveaux Blessés (Paris, Bayard, 2007) according to which the neurosciences refute the psychoanalytical conception of trauma. In cerebral lesions, two distinct phenomena co-occur: the anatomical and physiological destruction of part of the brain as a result of an external cause on the one hand, and on the other the way in which the subject experiences this catastrophe (pain or pleasure) which at the outset has nothing to do with him. The exterior has two distinct acceptations. Apparently, contingent factors can, via transference, transform the trauma. As Freud states in Evolution, chance encounters “rejuvenate cells”. This rejuvenation is not procreation, and it only works because it occurs in the neighbourhood of a risk of destruction. This “neighbourhood” should be envisaged differently in biology (symbiosis) and psychoanalysis (inventive capacity of the death drive, borrowing material from destruction). DiscussionFreud's thought in this text uses a vocabulary and in some instances concepts that are inadequate: 1. For instance, while the death drive and trauma in the psychoanalytic sense would require explicit reference to the opposition between exterior and interior for the psychic apparatus, he continues to deploy these notions without explicitly redefining them. 2. Again, his numerous references to the theory of evolution in biology are accompanied by numerous changes in direction on the issue of the homogeneity or the heterogeneity of the two fields, in which he explicitly recognises a mechanism that is very close, in the intrication of destruction and transformation, which later proves inventive. Every time Freud gives in to the illusion that he can discover a common origin for the living and drive, the ghost of Fliess turns up in the text. He then shakes him off with rather allusive violence. This is particularly prominent when he joins Schopenhauer with Flies to draw away from both at once, but without any explanation. He then takes on the role of a philosopher, making a detour via Plato's myth of Eros. His relationship with Fliess upsets his method, generally quite remarkable, of confrontation between clinical practice and hypothesis. But this “upset” in his thinking is also the subject matter of the discipline he created. ConclusionsThe epistemological and philosophical challenge is to consider the status of hypothesis in the clinical approach to sexuality and the formations of the unconscious. This is why psychoanalysis, although not a science, needs constant proximity with the sciences. The challenge in clinical practice is to approach the originality of psychoanalytic practice, which is in no way an “imperialistic” discipline, but provides itself with the means to explore and transform an aspect of reality: the link between pain, pleasure and culture.