Classical Hamilton-Jacobi theory, suitably interpreted in terms of a fundamental and irreducible concept of "guiding field", is proposed as the basis of classical physics, independent of and more fundamental than Newtonian mechanics. The "pilot-wave" approach is then seen as a natural unified basis for classical, quantum, and subquantum physics, whereby all interactions are seen as forms of EPR-entanglement. We attempt to clarify the emergence of standard quantum theory as an equilibrium phenomenology, thereby accounting for its "conspiratorial" relation with relativity theory, as well as clarifying its peculiar features with regard to "measurement". We emphasise the phenomenological nature of classical language, and the essentially illusory nature of the classically-inspired theory
of quantum "measurement" (the "Plato's Cave effect"}. A subquantum statistical mechanics and H-theorem are developed, establishing P=lYl2 as an equilibrium distribution.
The pilot-wave theory is extended in its scope. A field theory of massive "particles", which explains these in terms of "field lumps", is given, as well as a Grassmann field theory of spin. The Lorentz absolute 3+1 view of special relativity
is adopted, Lorentz symmetry being explained as a maximum-entropy equilibrium symmetry. This leads to an absolute 3+1 theory of electrodynamics in terms of a pure 3-vector potential, which avoids the troublesome time-component "nondynamical" degree of freedom. A similar approach is applied to gravitation, which drops from the outset the non-dynamical time-components of the metric. Subquantum nonlocality is assumed to provide an absolute 3+1 slicing of spacetime. leading to a straightforward pilot-wave theory of quantum gravity, which describes the evolution of absolute 3-space geometry in absolute time. This approach overcomes the fundamental conceptual problems of standard quantum gravity and quantum cosmology. Cosmological implications are discussed. The theory of measurement is extended to the subquantum domain, leading to the consideration of subquantum automata and enhanced parallel computation. It is shown how a subquantum automaton or "observer" could function as an essential
part of a "system", in a manner outside the scope of standard quantum theory. It is also shown that the pilot-wave theory is in principle experimentally distinct from standard quantum theory, in particular for finite-ensembles and in the
presence of residual disequilibrium or rare fluctuations. Various other aspects of the theory are also discussed. An attempt is made throughout to view the theory in an appropriate historical and philosophical perspective.
