In 1970 the mathematician John Conway defined a system with almost nothing in it. A grid of square cells, each either alive or dead. Four rules deciding which cells live, die, or are born in the next step, based only on how many neighbours each one has. That is the entire specification. It fits in a sentence. There is no further machinery.

What grows out of it is the surprise. From those four rules emerge stable structures, oscillators that pulse forever, and "gliders" — patterns that crawl across the grid as if they were objects with intent. Larger constructions appear: guns that fire gliders, patterns that copy themselves, arrangements that compute. The Game of Life is provably capable of universal computation. Anything a computer can do, a large enough Life grid can do, using only those four rules and the right starting pattern.

Conway did not design the gliders. Nobody did. They are emergent — consequences of the rules that no one wrote in directly and no one could have predicted by inspection. You have to run the system to find out what it produces. Simplicity at the bottom, unbounded complexity at the top, with no designer of the complexity in between.

This is the most important lesson a simulation gives a sceptic. The richness of our world is often used as an argument against it being computed: surely something this complex cannot run on rules. The Game of Life answers directly. A few rules and a large grid are enough for everything — including observers who wonder how rules this simple could have produced them.