 Hook worked primarily in the areas of the pragmatic theory of knowledge, ethical naturalism, and social and political theory. In regard to theory of knowledge, Hook believed that only the pragmatic account of knowledge, with its instrumentalist emphasis, provided an adequate explanation of the value ascribed to knowledge in human experience and a satisfactory answer to the question of why knowledge was important for human life. In regard to ethical naturalism, Hook argued that a naturalistic account of the origin and justification of ethical statements offered a critical yet justified and objective basis for moral decisions. In his defense of ethical naturalism, Hook carried out a sustained criticism of opposing theses. These theses included all forms of moral absolutism that were derived from inherited religious traditions or metaphysical systems of Idealism or Intuitionism. They also included the variants of what he considered to be moral relativism or moral nihilism, whether these were derived from arbitrary commitments as in Existentialist philosophy, or were supported as expressions of emotive attitudes as in Logical Positivism.