The Problem of Matter's Inherent Nature

Date of Award


Degree Type


Degree Name

Doctor of Philosophy (PhD)




Jonathan Bennett


Leibniz, Kant, Locke, Materialism, Atomists

Subject Categories



What distinguishes a pebble from an empty region of space of the same size? What is matter's inherent nature, the quality which fills space and in virtue of whose filling there is matter in space? Here I raise that question for a variety of metaphysical systems, from ancient atomism to contemporary scientific realism.

In the first chapter I argue that the secondary qualities can't serve as matter's inherent quality because they aren't physically basic, and each of the primary qualities is unqualified because it is either purely spatial (as are size and shape) or relational (as is motion) or dispositional (as are impenetrability, solidity and mass).

The second chapter is a survey which shows that philosophers typically want matter's nature to (1) be mathematizable; (2) explain change; (3) have a manifest basis if it is dispositional; (4) be monadic; (5) be determinate; (6) account for matter's permanence; (7) characterize discrete chunks of matter; (8) be an intensive quality; (9) not be dependent upon current physical theory; (10) be knowable and (11) be intelligible. This discussion sets the stage for the historical part of the dissertation, since I view the differences between philosophers like Newton, Leibniz, and Kant as due to differing beliefs about which of these constraints one should take as decisive.

Chapter three is a discussion of ancient atomism, where the concept of matter as "the full" as opposed to space, or "the empty," originated.

In chapter four I examine in detail Leibniz's arguments against the Cartesian position that matter is space and against the Newtonian position that matter is solidity or mass.

The fifth chapter is devoted to evaluating Leibniz's proposed substitute for mass, force. I argue that it can meet quite a few of the constraints, and offer a definition which gives the necessary and sufficient conditions for Leibnizian matter.

Chapter six is a presentation of Kant's theory as put forward in his Metaphysical Foundations of Natural Science. I examine Kant's arguments for the conclusion that matter would be impossible unless there were "repulsive force" and "attractive force" balancing one another in nature.

In the final chapter I offer a broadly Kantian solution to the problem.


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