The relation between the concepts of mind and brain has been the subject of philosophical analysis for a very long time, and many theories concerning the nature of that relation have been propounded. The problem dates back at least to the time of Plato, and in recent years philosophers seem increasingly compelled to attack it. In the 20th century a particularly strong approach has been along the lines of linguistic analysis, so that the manner in which language relates to the formulation of the problem in the first place is dealt with analytically, "therapeutically," and imaginatively. Approaches have been "common sensical" (Moore), "logistic or analytic" (Russell), grammatical (Wittgenstein), linguistic (Austin), and conceptual (J. L. Wisdom). The rewards of this approach have been considerable, particularly with respect to delimiting these various sorts of boundaries of our capacities for, and limitations with respect to, knowing.