Subject-Object Based Metaphysics is terminology used by the author Robert M. Pirsig with respect to the historically dominant form of metaphysics in Western philosophy. Pirsig claims that the use of subjects and objects as separate, distinct entities stems from the founding of modern intellectual discourse on the logic of "plus or minus." Things either are or aren't, and any further findings are considered non-empirical. The subjective side of thought is considered entirely non-empirical. Pirsig also notes that the subject-object metaphysics have distanced subjects from objects in places where they are inexorably linked. Pirsig uses the notion of "quality" to re-unify the two terms using the Metaphysics of Quality.