A duty is a legal obligation owed to another, and to which that other person has a corresponding legal right.For example, in the case of the psychotherapist-patient legal relationship, therapists actually have several duties that they owe, one of which is the duty to maintain confidentiality.(Another duty that clinicians are familiar with is the duty to protect.)To reiterate, confidentiality is a kind of duty, one of many that certain persons have.A privilege, on the other hand, is another kind of a legal right, but one that usually takes the form of an exemption from the duty to do something.