Created: February 14, 2021
Modified: October 02, 2021
Modified: October 02, 2021
generalization
This page is from my personal notes, and has not been specifically reviewed for public consumption. It might be incomplete, wrong, outdated, or stupid. Caveat lector.- Fundamentally, where does generalization come from?
- causality: a model may generalize because it has discovered the true mechanism, or an abstract mechanism that captures some of the true mechanism.
- But not all generalization comes from causality. Linear regression can generalize even when we know that the matrix multiplication is not the causal process underlying the data. Sure, the true causal process viewed from some angle might produces results that are roughly linear in some input, so we can think of linearity as an 'abstract mechanism', but that doesn't feel like a full or satisfying story.
- Generalization can come from smoothness. Things in physics move smoothly, so almost anything produced by a physically realistic causal mechanism will be mostly smooth. Linearity, or (more generally) polynomials of limited degree, is a form of smoothness assumption.
- The no free lunch theorem: without assumptions, generalization is impossible.