Freud's careful attention to clarity of terminology is contrasted with present tendencies toward vagueness in the use of the term regression. Pasche undertakes a critical evaluation of the concept, and emphasizes the theoretical and clinical importance of distinguishing between temporal and topographical, complete or incomplete regression. Sexual perversions, sleep, coital orgasm, and the primary experiences of artistic creativity are examples of 'perfect' (complete) temporal regression; all other instances of regression are categorized as incomplete and complicated by heterogenous elements from various developmental sequences, as well as their antero- and retrogressive elaborations.