In ethics consultations and in dealing with ethical issues as they arise in health care practice, we often draw on reasoning used in previous situations. Coherence of our ethical judgment relies on drawing upon and and being consistent->consistency with previously-adjudicated cases.
In ethics work, we often focus on similarities in the values and principles pertinent to a situation and similarities in features of the situation that determine which values and principles are pertinent.
The choice of comparator often determines the focus or direction of a particular consultation.