Middle Size Matters, but it is Lego Bricks all the Way Down

This paper develops compositional functionalism, an account of explanation within the primitive ontology framework that reconciles compositional grounding with the autonomy of the special sciences. I argue that functional explanations are appropriate within a given level, while compositional and dynamical explanations account for why those explanations work across levels. In this way, compositionality and functionalism are complementary rather than competing. The view explains why effective ontologies emerge at specific scales, why higher-level laws are stable yet only approximately exceptionless, and why compositional precision matters at microscopic levels but becomes dispensable at macroscopic ones. I further argue that this framework extends to the quantum domain through the pilot-wave theory, which restores a constructive account of matter in spacetime. The world remains “Lego bricks all the way down,” but the patterns formed at each level acquire their own explanatory significance.