A review is given of the development of ideas concerning the transport and distribution of ionospheric plasma in the magnetosphere. An unresolved dichotomy in these ideas is identified, in which two incompatible explanations have been given for the low plasma densities outside the plasmasphere, the convection/hot solar plasma model, and the convection/loss model. This dichotomy reveals a fundamental unresolved problem in magnetospheric physics whose resolution is essential if we are to adequately understand the transport of mass, momentum and energy through the magnetosphere, and the resulting contributions of terrestrial and solar plasma sources. Recent progress in understanding global ionospheric outflows is reviewed for clues which might help resolve this problem. Observations are compared with theoretical concepts dealing with (1) the low-altitude collisional and chemical processes affecting the character of ionospheric outflow, (2) the ambipolar outflow of plasma in the collisionless region above, and (3) the acceleration of ionospheric plasma by macroscopic magnetospheric electric fields associated with structured convection. We appear to need a hybrid model of magnetospheric plasma in which terrestrial plasma is both lost into the solar wind, and energized and trapped within the magnetosphere, inflating the geomagnetic field and excluding cold plasma from conjugate regions.