Build-From-Scratch Pedagogy

andrej karpathy’s teaching move: build the minimal version from scratch to understand the thing. micrograd before PyTorch, nanoGPT before the transformers library. The toy implementation IS the explanation — every step visible, no “it can be shown that.”

Root

richard feynman’s last blackboard: “What I cannot create, I do not understand.” Karpathy is an explicit disciple. The toy build is step 4 of the feynman technique made executable: create the thing, and the creation IS the understanding.

When to use it

• Understanding complex computational systems (how transformers work, how an event loop runs).
• Debugging a black box — rebuild the minimal reproduction instead of reading logs and guessing.
• Evaluating whether an abstraction earns its keep — can you build the 50-line version that does the same thing?

How it fits the engineering stack

Complements feynman technique (plain-language explanation) and powers tracer bullets at the learning level: the minimal build is the tracer bullet for understanding. Aligns with karpathy four guidelines #2 (simplicity first) and #4 (goal-driven — the working toy IS the verifiable success criteria).

Related

feynman technique, first principles thinking, tracer bullets, tdd with agents.