A complete global analysis of spatially-flat, four-dimensional cosmologies
derived from the type IIA string and M-theory effective actions is presented. A
non--trivial Ramond-Ramond sector is included. The governing equations are
written as a dynamical system. Asymptotically, the form fields are dynamically
negligible, but play a crucial role in determining the possible intermediate
behaviour of the solutions (i.e. the nature of the equilibrium points). The
only past-attracting solution (source in the system) may be interpreted in the
eleven-dimensional setting in terms of flat space. This source is unstable to
the introduction of spatial curvature.
Comment: 13 pages, 4 Postscript figures, uses graphics.sty, submitted to Phys.
Subjects: High Energy Physics - Theory; Astrophysics; General Relativity and Quantum Cosmology