Anxiety
The philosopher Søren Kierkegaard, in "The Concept of Anxiety" (1844), described anxiety or dread associated with the "dizziness of freedom" and suggested the possibility for positive resolution of anxiety through the self-conscious exercise of responsibility and choosing. In "Art and Artist" (1932), the psychologist Otto Rank wrote that the psychological trauma of birth was the pre-eminent human symbol of existential anxiety and encompasses the creative person's simultaneous fear of – and desire for – separation, individuation, and differentiation.
David H. Barlow
As Barlow's ideas of the nature and origins of anxiety started to become more elaborate, he published a series of books that delineated the results from his research and advocated for a more empirical scientific approach to clinical psychology. In 1985, he published the first edition of the "Clinical handbook of psychological disorders: A step-by-step treatment manual", explicating evidence based practices. Aggregating his ideas from this period of extensive research, Barlow published what the "American Psychologist" deemed as his "most influential book", "Anxiety and its disorders: The nature and treatment of anxiety and panic".