  A defining feature of holographic dualities is that, along with the bulk
equations of motion, boundary correlators at any given time t determine those
of observables deep in the bulk. We argue that this property emerges from the
bulk gravitational Gauss law together with bulk quantum entanglement as
embodied in the Reeh-Schlieder theorem. Stringy bulk degrees of freedom are not
required and play little role even when they exist. As an example we study a
toy model whose matter sector is a free scalar field. The energy density (\rho)
sources what we call a pseudo-Newtonian potential (\Phi) through Poisson's
equation on each constant time surface, but there is no back-reaction on the
matter. We show the Hamiltonian to be essentially self-adjoint on the domain
generated from the vacuum by acting with boundary observables localized in an
arbitrarily small neighborhood of the chosen time t. Since the Gauss law
represents the Hamiltonian as a boundary term, the model is holographic in the
sense stated above.
