  We argue that the geodesic hypothesis based on auto-parallels of the
Levi-Civita connection may need refinement in theories of gravity with
additional scalar fields. This argument is illustrated with a re-formulation of
the Brans-Dicke theory in terms of a spacetime connection with torsion
determined dynamically in terms of the gradient of the Brans-Dicke scalar
field. The perihelion shift in the orbit of Mercury is calculated on the
alternative hypothesis that its world-line is an auto-parallel of such a
connection. If scalar fields couple significantly to matter and spinless test
particles move on such world-lines, current time keeping methods based on the
conventional geodesic hypothesis may need refinement.
