Abstract
This paper explores part of the making of a cyberneticist. It examines Walter Pitts' contribution to two of McCulloch's most celebrated publications, 'A Logical Calculus of the Ideas Immanent in Nervous Activity' and 'How we Know Universals: the Perception of Auditory and Visual Forms'. What we find, in part, is that Pitts provided mathematical clarity and rigor to McCulloch's views on psychons and circular causality.