Abstract
It has long been recognized that the insights of Russian thought are more often to be found in literature and literary criticism, than in technical philosophy. Simon Frank, however, is a twentieth-century Russian emigre who demonstrates considerable agility in the labyrinths of philosophical inquiry. In The Unknowable, first published in 1939, his basic thesis is that philosophy achieves its ultimate when it recognizes the limits of the rational. It is precisely the transrational, the "unknowable" in rational terms, which is most important to man. Hence, true philosophy inevitable leads into the religious dimension.