Recursive organization and contrastive relations in the structure of language are discussed. A qualitative schema of developmental progression which represents a "complex sequence model" is elaborated in which the operations of earlier stages are incorporated into later ones, even though their significance is successively reduced. Levels of development, both recursive and contrastive are given—level 1, characterized as "monoremes," level 2 as "duoremes," level 3 by the acquisition and utilization of classes, level 4 by apprehending relations of relations--and each level is divided into sublevels. Level 1 is preceded by a prelingual stage. The recursive levels are given as prelingual differentiation (level 0), extralingual recursion and intralingual recursion (level 1), categorical recursion (level 2), and semantic recursion (level 3). The contrastive relations are given as constancy of phenomena (level 0), monadic and diadic operations (level 1), triadic operations (level 2), and tetradic operations (level 3).
