Any of the three classical rules of drama: unity of action (nothing should be admitted not directly relevant to the development of the plot), unity of place (the scenes should be set in the same place), and unity of time (all the events should be such as might happen within a single day).
The form of consensus in a Quaker meeting for business which signals that a decision has been reached. In order to achieve unity, everyone who does not agree with the decision must explicitly stand aside, possibly being recorded in the minutes as doing so.