The free energy principle (FEP) is a new paradigm that has gain widespread interest in the neuroscience community. Although its principal architect, Karl Friston, is a psychiatrist, it has thus far had little impact within psychiatry. This article introduces readers to the FEP, points out its consilience with Freud's neuroscientific ideas and with psychodynamic practice, and suggests ways in which the FEP can help explain the mechanisms of action of the psychotherapies.