The largest disparity between position in the social hierarchy of Western medicine is between the patient and the physician. The patient/physician interaction is critically shaped by the rigidity of the social hierarchy. In describing the nature of the patient/physician relationship, Parsons lays out four distinct features that establish and maintain a particular form of the subordinate/superior relationship, most commonly expressed in terms of power/authority.
Before going further, an extremely important distinction must be drawn. Power and authority are, categorically, not the same things. For instance, in at least one form, the legitimization of authority allows one to exercise more power. Authority therefore enhances elements like one’s reputation or one’s social standing. Authority, also, could be viewed as an entirely different form of power. Whereas power may stipulate the explicit use of force/coercion (i.e. violence), authority may stipulate a softer version of that with similar end results but without the use of force/coercion. Instead, psychological mechanisms and tools may be utilized. I don’t want to go too far down the rabbit hole on this, but suffice it to say they are conceptually and logically distinct and should be kept that way for current purposes.
In this case, the physician is bestowed with authority through his/her extensive knowledge of the human body, coupled with the recognition of the former by the social structure known as medical school. The authority of the physician allows him/her to suggest, recommend, and, in some cases, command the patient to complete or permit certain actions.