The medium is the message

Marshall McLuhan argued in 1964 that the form of a medium shapes us more deeply than any particular content it carries. The printing press changed European thought not through any one book but by making literacy itself ordinary.

Alan Kay took this seriously as a design brief. If the computer is a new medium — and Kay believes it is the first metamedium, able to simulate every prior medium and invent new ones — then the real question is not what content we'll put on it, but what new kinds of thought it makes possible, and whether we are learning to think in it the way past generations learned to read.

This is the deep link between McLuhan, the Dynabook, and the whole tools-for-thought tradition: the worry that we are using a thinking medium mostly for consumption.