his introductory essay - introduced their work into this country. [ 83 ] A more recent contributor to the development of a European version of existentialist psychotherapy is the British-based Emmy van Deurzen . Anxiety's importance in existentialism makes it a popular topic in psychotherapy . Therapists often offer existentialist philosophy as an explanation for anxiety. The assertion is that anxiety is manifested of an individual's complete freedom to decide, and complete responsibility for the outcome of such decisions. Psychotherapists using an existentialist approach believe that a patient can harness his anxiety and use it constructively. Instead of suppressing anxiety, patients are advised to use it as grounds for change. By embracing anxiety as inevitable, a person can use it to achieve his full potential in life. Humanistic psychology also had major impetus from existentialist psychology and shares many of the fundamental tenets. Terror management theory , based on the writings of Ernest Becker and Otto Rank , is a developing area of study within the academic study of psychology. It looks at what researchers claim are implicit emotional reactions of people confronted with the knowledge that they will eventually die. Logical positivist philosophers, such as Rudolf Carnap and Alfred Ayer , assert that existentialists are often confused about the verb "to be" in their analyses of "being". [ 84 ] Specifically, they argue that the verb is transitive and pre-fixed to a predicate (e.g., an apple is red ) (without a predicate, the word is meaningless), and that existentialists