|Principles of geometry used in composition, sketch by Baldassare Peruzzi|
In order to produce a desired effect, a desired end, one has only two choices to achieve that end, one either comes to understand the principles which operate to produce that end, or one relies on the application of a set of rules to produce that end.
The former is akin to the practice of ethics, where one seeks to understand the principles of justice, temperance and the other virtues, to put them into practice in an infinite number of circumstances. The intention is to grasp a universal principle, which when properly understood can be applied in each particular circumstance in a way proper to that circumstance.
The alternative is the application of rules. Rules as such are not universal, they don't refer to every circumstance but to particular circumstances, and in art are the creation of particular forms. Rules are created according to principles, and for the greater part of circumstances they serve to produce the same effects as the application of principles. One applies the rules, and for the greatest part of the time, they produce the exact end which you intend from the beginning.
However rules do from time to time, by an absolute rigid application, produce the opposite intended end. The rule is not flexible as it applies absolute to particular circumstance, whereas principles applied seeking the ultimate end, allow for more flexibility, that is "breaking the rules"
When one unmoors oneself from the application of principles, the only alternative is to use rules to create the end. If one seeks however to unmoor themselves from the application of rules, they must return to the principles to produce the end. If however one is unmoored both from rule and from principle then the end of the artist is only randomly produced, the artist is left to pick and choose willy-nilly from any number of alternatives, and only by chance would ever produce his end.