Substance and Intelligibility in Leibniz's Metaphysics (review)

This very fine book takes as its point of departure a tension that runs throughout Leibniz's philosophy. That Leibniz sometimes seems to speak with more than one voice on issues metaphysical will come as no surprise to his readers. The tension identified by Palkoska, however, is not to be found in the content of Leibniz's metaphysical doctrines, but instead at a more fundamental level: his questioning the very possibility of a scientia of being. Casting into doubt the project of metaphysics runs orthogonally to a philosophical system renowned for its extravagantly speculative pronouncements about substance, monads, God, et al. The objective of this book is to show how Leibniz reconciles his skepticism about the possibility of metaphysics, conceived along certain lines, with his dogged commitment to discovering the nature and structure of substance.

Palkoska starts by investigating Leibniz's conception of the method of metaphysics, and why this conception generates problems for any metaphysical inquiry. Following Aristotle, Leibniz takes metaphysics to be the science of being qua being, where "science" is intended as a demonstrative body of knowledge that proceeds a priori and deductively from first principles, establishing conclusions that can be known with certainty. The object of this science is ens, which "is properly located within the realm of possibility" (23). Expanding on this, Palkoska contends that ens pertains not to objects themselves, but to concepts of objects, or, what comes to the same thing, to the divine attributes, or divine ideas. Restricted to things considered as possible, metaphysics is concerned with analyzing the internal consistency of concepts, which entails resolving complex concepts into their primitive parts. The objective of metaphysics is to provide an essential real definition of an ens, a definition that is a complete enumeration of the primitive concepts that enter into the concept of the thing, and that demonstrates the possibility of the thing in question by showing that there is no incompatibility among those primitive concepts. It is this requirement that renders metaphysics deeply problematic, for given the epistemic limitation of humans, such definitions lie beyond our cognitive grasp. If the human mind is inadequate for providing the types of definitions required by metaphysics, then it is inadequate for arriving at a scientia of being.

How can Leibniz secure the possibility of a science of metaphysics? On Palkoska's reading, the key gambit in Leibniz's strategy is to relax the requirement for real definitions, pursuing in its place the "basic nominal definition of substance," and pushing this nominal definition to the maximal degree of distinctness allowed by our cognitive faculties. Leibniz relinquishes the ideal of a complete enumeration of the primitive concepts of an ens, being content with a delineation of those concepts that are primitive quoad nos. Lest this be an exercise in tilting at metaphysical windmills, the reality of these definitions is to be secured a posteriori by a kind of inner-experience, viz. by self-reflexive knowledge.

The remainder of the book is devoted to a meticulous analysis of the nominal definition of substance quoad nos. Palkoska focuses on three of Leibniz's characterizations of substance: substance as a per se unity, a concrete entity that is an ultimate subject of predication, and a complete being falling under a complete concept. The "meta-criterion" that underwrites and gives unity to these various characterizations is self-sufficiency. Palkoska shows how Leibniz articulates this meta-criterion without lapsing into a kind of Spinozism according to which there is only one self-sufficient substance. Of particular interest to Leibniz scholars is Palkoska's discussion of the vexatious issue of the reality of corporeal substances. After an investigation into what it means for something to count as a per se unity, Palkoska concludes that this criterion issues in a "radically reductive ontology of simple substances"—immaterial monads—with corporeal substances being relegated to the status of well-founded phenomena (122), though he suggests that Leibniz sometimes stepped back from this view.

The most obvious objection...