The protean nature of the computer is such that it can act like a machine or like a language to be shaped and exploited.

Kay is pointing to what he and other early personal-computing pioneers saw as the computer’s defining trait: it is not a single-purpose device but a “meta-medium” whose behavior can be reconfigured by software. In one mode it resembles a conventional machine—fixed procedures, automation, and efficiency. In another it functions like a language: a symbolic system users can extend, recombine, and use to express new ideas. The quote underscores a central theme in Kay’s work on Smalltalk and the Dynabook vision: empowering people (especially learners) to shape computational tools, not merely operate them, and treating programming as a medium for thought and invention rather than only engineering.