It’s a slightly complex story. I started working in physics when I was an early teenager. Mostly I worked on particle physics, but I also thought a lot about the foundations of thermodynamics and statistical physics. And around 1978 I got very interested in the question of how complex structure arises in the universe—from galaxies on down.

Soon thereafter, I became very involved in computer language design—creating a precursor of what is now Mathematica—and was very struck by the process of going from the simple primitives in a good language, to all of the rich and complex things that can be created from it.

In 1981 I felt like taking a little break from my activities in doing physics, computing and starting a company. I decided to do something “fun”. I thought I would look back at my old interests in structure formation. I realized that there was the same central question in lots and lots of fields: given fairly simple underlying components, how does such-and-such a complex structure or phenomenon arise?

I decided to try to tackle that question—as kind of an abstract scientific question. I think what I did was very informed by my experience in creating computer languages. I tried to find the very simplest possible primitives—and see what happened with those. I ended up studying cellular automata, and in using those discovered what I thought were some pretty fundamental facts about how complexity can arise.