Is Cognition Discrete or Continuous?
Although I hate to haggle over words, Harnad’s use of `analog’ confuses a number of issues. The problem begins with the phrase `analog world’ in the title, which does not correspond to any technical or nontechnical usage of `analog’ with which I’m familiar. Although I don’t know precisely what he means by `analog’, it is clearly related to the distinction between analog and digital computers, so I’ll consider that first. In traditional terminology, analog computers represent variables by continuously-varying quantities, whereas digital computers represent them by discretely-varying quantities (typically, voltages, currents, charges, etc. in both cases). Thus the difference between analog and digital computation lies in a distinction between the continuous and the discrete, but it is not the precise mathematical distinction. What matters is the behavior of the system at the relevant level of analysis. For example, in an analog computer we treat charge as though it varies continuously, a
