Purpose - To reconstruct the way in which the difference of analog vs digital was introduced in the 1940s and to investigate why this difference was so fundamental to the whole cybernetic epistemology. Design/methodology/ approach - A close reading of the discussions about the terms "analog" and "digital" at the Macy-Conferences (held during 1946-1953) reveals how cybernetic discourse is founded on a suppression of the "real" (i.e. the physical, continuous, material, analog) by the "symbolic" (i.e. the artificial, discrete, logical, digital). Findings - First, the difference between "analog" and "digital" resembles the Kantian difference of "senses" and "reason". Together they form the "illusionary" function, which a digital-oriented cybernetics tries to abandon. Second, the attempt to get rid of this illusion produces itself a "cybernetic illusion", that replaces the anthropological illusion established (according to Michel Foucault) in late 18th century. Originality/value - Showing that Heinz von Foerster's work could be seen as an attempt to establish a balance of power between analog and digital, and to respect the illusionary function of cybernetic knowledge.