What the proof actually said

Minsky and Papert proved that this design had a ceiling.

They said nothing about whether a different design might escape it. Nobody had. The question was completely open. And yet the field acted as if it had been answered.

There's a name for this kind of mistake: jumping from "this version failed" to "none of them will." It happens in science, in business, in medicine. It happened here.

A small group of researchers read the proof carefully and noticed the gap. The book killed one design. It didn't kill the idea. They kept working, quietly, with little funding, through the 1970s and into the 1980s, on designs nobody had tried yet.

But before we get there: what exactly was the limit? What could the Perceptron actually do — and why couldn't it do more?