The standard gloss of “metaphysics”—

1. Metaphysics works to justify the ultimate assumptions of the sciences, and
2. Metaphysics is unique in that it contains no unjustified premises.

(1) cannot be right since empirical laws become justified in only two ways—by not being falsified in experience, and by being derivable from a more comprehensive (and abstract) science. We can, for example, derive the laws of chemistry from the deeper ones of quantum mechanics; and what we assume in geology can be proved in physics.

(2) is the more interesting claim. Can any intellectual activity proceed without assuming contentful (non-analytic) propositions? Logic seems to qualify. Math as formalism requires the Peano axioms; as logicism, it qualifies insofar as set theory is valid, predate logic is a non-optional condition of rationality, and the identification of numbers with sets is surely unobjectionable.

Metaphysics makes claims about the ground and conditions of presence, quiddity, and speaking about these—about the conditions that must be in place before anything can begin. Metaphysicians like J. F. Ferrier, F. H. Bradley, and Josiah Royce argued that, while totally presumption-less thinking cannot occur, something like the absolute does shine through—in the form of premises that are self-reinstating.