We define the general circulation as flow with large spatial and long time scales, for which the earth's rotation is critical in the momentum balance. The dynamical basis for our approach to the general circulation has as its cornerstones: geostrophic and hydrostatic balance, Ekman response to wind driving, the large-scale Sverdrup potential vorticity balance, various western boundary current theories, and a concept of eddy viscosity. Each of these is defined and described below in this section. With these ideas have been constructed theories of the wind-driven and abyssal circulation for one layer oceans; summaries can be found in Gill [1982], Pedlosky [1978], the various papers in Abarbanel and Young [1987], and the new descriptive text by Tomczak and Godfrey [1994]. These ideas have a long history and remain central to our thinking, because they appear to explain the features which we associate with the general circulation even though specific tests of their validity have been somewhat lacking.