PHYSICS.

If the universe’s entropy “tends toward its maximum” then, according to Clausius, the more the universe draws close to that limit state, the more the opportunities for new changes disappear. When that state is reached, no further change would occur, and the universe finds itself in a “persistent state of death” (Clausius, 1865, In: Locqueneux, 2009, p. 249). These considerations make it possible to reread Freud’s hypothesis of the death drive in the light of the physics model, which had from the outset been the epistemological paradigm for his initial theoretical thinking. If we apply to living organisms this tendency of the universe toward a state of equilibrium, defined by the irreversible absence of all discernible motion and all difference in tendency – in other words equivalent to a definitive death – we can envisage a closed system consisting of the unit “organism-environment.” The second law implies that within this system the different levels of energy tend toward equaling out, in such a way that the final state would be a state of equilibrium. The state toward which the system would tend would therefore be equivalent to “the reduction of the organism’s internal energy that returns it to the inorganic state” (Laplanche and Pontalis, 1967a, p. 326). Now, let us recall that in 1920, Freud describes the conservative or “regressive” character of the death drives as originating in “the coming to life of inorganic substance” (Freud, 1920, p. 44) and that it “seek(s) to restore the inanimate state” (Freud, 1920, p. 44). If the definition of the death drive as the tendency of the living organism to return to an inorganic state can, in the first instance, “seem an aberration from the point of view of the life sciences – in so far as that it seeks to infer an organism with its vital aptitudes, its adaptative functions, its energy levels, from a principle that is the negation of all constant level of difference” (Laplanche and Pontalis, 1967a, p. 328) – it appears much more coherent within a physics model. Furthermore, it should be pointed out that the first ambition of the Helmholtz School, to which Freud was heir, had as specific objective the application of the physical laws of thermodynamics to the study of living organisms.

The thermodynamics that inspired Freud described how systems reached an equilibrium characterized by a maximum of entropy. In contrast1, as Prigogine (1978, 1981) pointed out, when systems are far from equilibrium and driven by a large energy current, entropy may decrease and ordered patterns form. Current research focuses precisely on the self-organization of systems far from equilibrium. The neuronal dynamics, with the discharges that Freud envisaged, find echo in the theory of self-organized criticality (Bak, 1996; Vespignani and Zapperi, 1998). Major advances were achieved by adapting the evolution equations of statistical physics (Fokker–Planck equations) to out-of-equilibrium, open systems (Seifert, 2005; Tomé, 2006; Esposito et al., 2009; Jeffery et al., 2019). It is quite remarkable, in view of Freud’s affinity for Helmholtz work, that a thermodynamic potential, the free energy, appears to be the quantity that best describes the steady state of a system driven out of equilibrium because of its strong interactions with its environment (Jarzynski, 1997; Evans and Searles, 2002; Friston, 2019). Based on these new ideas, the “death drive” might be recast as a natural tendency of certain out-of-equilibrium systems to reach a steady-state characterized by a minimization of free energy. Indeed, there have been attempts to connect Freudian notions of free (unbound) energy to the variational free energy that figures in theoretical neurobiology and statistical mechanics (Carhart-Harris and Friston, 2010). If this is possible, it would mean that the death drive might now be cast in a way that is formally similar to the way Newtonian mechanics was recast in a “principle of least action.” This would constitute a major advance in Freud’s “Project for a Scientific Psychology.”