In 1972, the future Nobel Prize winner in physics Philip Anderson published an article in Science entitled "More is Different", in which he set out the concept of emergence in a remarkably clear manner: the behavior of assemblies of interacting particles cannot be understood as a simple extrapolation of the behavior of isolated particles. On the contrary, original and surprising behaviors can emerge, and understanding them requires specific concepts and new tools. The whole is not greater than the sum of its parts, it is different.
Anderson had in mind, in particular, the astonishing collective behaviors of condensed matter such as superfluidity, which does not exist at the atomic level, and can only appear at the macroscopic level. This phenomenon of emergence concerns many fields outside physics: the collective behavior of neurons (memory, consciousness), the "murmurings" of starlings, social movements, economic crises, financial panics...
I thought a symposium on this theme would be a perfect epilogue to my lecture on the links between statistical physics - which is precisely the science of emergence - and the social sciences. My hope is that, for two days at the Collège de France, physicists, economists and mathematicians specializing in these ideas will be able to talk to each other, leading, who knows, to the emergence of new research directions.