Metaphysics
Physics is the scientific investigation of the fundamental nature of physical being. Metaphysics—at least within that tradition that traces itself back to Aristotle's eponymous treatise—is the philosophical investigation of the even more fundamental nature of being as such. Metaphysics is concerned with the contours of the categories of entity postulated or presupposed by any possible, acceptable, account of the world, whether of the physical world or of any other aspect of the world. The task of metaphysics is to lay out a complete, coherent ontology, embracing all that is necessary to capture the correct account of the world in any of the special inquiries—whether they be empirical, mathematical, modal, or moral.
The Changing Methods of Metaphysics
Traditionally, metaphysics was practiced as a top-down, a priori discipline, with Euclidean geometry as its model. The metaphysician begins with self-evident principles of a highly general nature, together with appropriate definitions, and proceeds to draw out the necessary consequences.
This approach is clearly exemplified in the work of two prominent eighteenth-century metaphysicians, Gottfried Wilhelm Leibniz and Benedict (Baruch) de Spinoza. Leibniz spun metaphysical gold out of the dross of the principles of noncontradiction and sufficient reason: His entire Monadology (1965), replete with an infinite collection of possible worlds, with the actual world (the best of all possible worlds) consisting of a myriad of mutually reflecting, simple, mind-like substances.
