 The inward/outward looking nature of the field of philosophy of education alluded to above makes the task of delineating the field, of giving an over-all picture of the intellectual landscape, somewhat complicated (for a detailed account of this topography, see Phillips 1985, 2010). Suffice it to say that some philosophers, as well as focusing inward on the abstract philosophical issues that concern them, are drawn outwards to discuss or comment on issues that are more commonly regarded as falling within the purview of professional educators, educational researchers, policy-makers and the like. (An example is Michael Scriven, who in his early career was a prominent philosopher of science; later he became a central figure in the development of the field of evaluation of educational and social programs. See Scriven 1991a, 1991b.) At the same time, there are professionals in the educational or closely related spheres who are drawn to discuss one or another of the philosophical issues that they encounter in the course of their work. (An example here is the behaviorist psychologist B.F. Skinner, the central figure in the development of operant conditioning and programmed learning, who in works such as Walden Two (1948) and Beyond Freedom and Dignity (1972) grappled—albeit controversially—with major philosophical issues that were related to his work.) 