Chapter 12: The Principle of Computational Equivalence

Section 3: The Content of the Principle

[Construction of] universal objects

A more direct way to create a universal object is to set up, say, a 4D array in which two of the dimensions range respectively over possible 1D cellular automaton rules and over possible initial conditions, while the other two dimensions correspond to space and time in the evolution of each cellular automaton from each initial condition. (Compare the parameter space sets of page 1006.)

From Stephen Wolfram: A New Kind of Science [citation]