  F-theory in its most general sense should be a theory defined on a
worldvolume of higher dimension than the worldsheet, that reproduces string
results perturbatively but includes nonperturbative supergravity solutions at
the first-quantized level. This implies that in some sense it should contain
the same oscillator modes as the string but an enlarged set of zero-modes. In
this paper we concentrate on the higher-dimensional properties of the
worldvolume (rather than those of spacetime): "Ghost" dimensions are added to
the worldvolume, as might be expected in a "zeroth-quantized" approach to the
constraints on its higher bosonic dimensions, by adding equal numbers of
bosonic and fermionic dimensions to the worldsheet.
