"What is fundamental?" Thales— said by many to be our first philosopher and astronomer— concluded that reality exists through an underlying fluid. However, in those days there were no super-conducting fluids, and no quantum, relativistic or string theoretic field theories in terms of which to think. Thales simply thought in terms of water. Close enough. Today that would be the fluid dynamics of fields. However, Thales also thought in terms of "agency" as we would term it today in behavioral economics, experimental and mathematical game theory.
Lee Bloomquist