Information processing depends upon the use of physical degrees of freedom. The use of physical degrees of freedom leads to fundamental limitations on information handling. Computihg must be dissipative. The sources of dissipation in turn generate noise. The computing process, however, can be made arbitrarily immune to this noise, at the expense of very slow computing. Computing requires electrically accessible cooperative phenomena in which the information bearing degree of freedom is spread out over many particles, associating a large thermal reservoir with the information bearing degree of freedom. The cooperative phenomena thus utilized in computing include not onty t h e normally called “cooperative,” but also the very similar behavior encountered in active dissipative bistable circuits. The analogy between active circuits and ordinary cooperative phenomena is discussed both at the macroscopic and the microscopic level. Active circuits exhibit phenomena which are equivalent to phase transitions, soft modes, and critical fluctuations. © 1971, Taylor & Francis Group, LLC. All rights reserved.