  Despite the importance of the path integral, there have been relatively few
attempts to look to the Lagrangian for a more realistic framework that might
underlie quantum theory. While such realism is not available for the standard
path integral or quantum field theory, a promising alternative is to only
consider field histories for which the Lagrangian density is always zero. With
this change, it appears possible to replace amplitudes with equally-weighted
probabilities. This paper demonstrates a proof-of-principle for this approach,
using a toy Lagrangian that corresponds to an arbitrary spin state. In this
restricted framework one can derive both the Born rule and its limits of
applicability. The fact that the Lagrangian obeys future boundary constraints
also results in the first continuous, spacetime-based, hidden-variable
description of a Bell-inequality-violating system.
