Machine Phase

Agüera y Arcas's name, in the What Is Intelligence? lecture, for the state a soup of random programs enters once replicators take over. In the Computational Life experiment, 64-byte Brainfuck strings are paired and run at random; for millions of interactions almost nothing executes, then replicators appear, operations per interaction climb into the thousands, and the soup abruptly becomes compressible. He reads that Kolmogorov-complexity drop as a phase transition, "like a gas" before, "machine phase, or computronium, or life" after. The book keeps only "computronium," Margolus's coinage widened to life's computational state on any substrate, adding that this phase must be lumpy, since uniform matter cannot compute. The term carries the inference that computation is an attractor: reproduction requires a program, so the moment is random but the transition inevitable. It underwrites Dynamic Stability and the book's definition of Life; Tripaldi's Substrate Agency contests the substrate indifference it assumes.