Several concerns, both theoretical and empirical, have arisen in response to the ascendancy of ACT. One major theoretical concern was that the primary authors of ACT and of the corresponding theories of human behavior, relational frame theory (RFT) and functional contextualism (FC), recommended their approach as the proverbial holy grail of psychological therapies. Later, in the preface to the second edition of "Acceptance and Commitment Therapy", the authors clarified that "ACT has not been created to undercut the traditions from which it came, nor does it claim to be a panacea." Psychologist James C. Coyne, in a discussion of "disappointments and embarrassments in the branding of psychotherapies as evidence supported", said: "Whether or not ACT is more efficacious than other therapies, as its proponents sometimes claim, or whether it is efficacious for psychosis, is debatable". The textbook "Systems of Psychotherapy: A Transtheoretical Analysis" provides criticisms of third-wave behaviour therapies including ACT from the perspectives of other systems of psychotherapy.