Book: Metaphysics

Scope and Aim
Metaphysics seeks the highest kind of knowledge, wisdom that grasps the first principles and causes of things. Human beings naturally desire to know, but genuine wisdom knows why things are as they are, not merely that they are. Philosophy at this level studies being insofar as it is being, not any particular kind of being. It also examines what it is to explain, what counts as a cause, and what must be presupposed for knowledge to be possible.

Being and Its Many Meanings
“Being” is said in many ways, yet these ways are ordered toward a primary meaning. The focal sense is substance (ousia), the independent “what it is” to be a thing, to which other senses, such as quantities, qualities, relations, or accidental attributes, are referred. Because being is analogical, a single science is possible: it studies what belongs to beings as beings, including unity, sameness and difference, contraries, priority, and posteriority. This inquiry also identifies the most basic principles without which talk about anything collapses, especially the principle of non-contradiction.

Substance, Essence, and Definition
The investigation centers on what substances are. A substance is what is neither predicated of a subject nor present in a subject; it is the ground of other predications and the bearer of change. The essence or “what-it-was-to-be” (to ti ēn einai) is what a correct definition captures. Definitions aim at form rather than at a mere heap of properties. Universals, however, cannot be primary substances, for a universal applies to many, while a substance is this particular. The upshot is that concrete substances are composites of form and matter: matter as the underlying potentiality to be many things, form as the actuality that makes a thing the kind of thing it is. The form is primary in account and, in many cases, in being.

Causes and Explanations
Explanation requires appeal to four kinds of causes: material (that out of which), formal (that by which it is what it is), efficient (the source of change), and final (that for the sake of which). Earlier thinkers often fixated on one cause, material elements for some, numbers or separable forms for others. A satisfactory account integrates all four where appropriate. This framework underwrites both natural change and the stability of knowledge, showing how unity arises in diverse things through shared forms and ends.

Potentiality and Actuality
A central distinction clarifies change and persistence: potentiality (dunamis) and actuality (energeia or entelecheia). Matter bears potentials; form is their realized act. Change is the actuality of what exists potentially, insofar as it is potential. Although potentiality is temporally prior in some cases, actuality is prior in account and substance: what is perfect, complete, and fully real grounds the becoming of what is incomplete.

Critique of Separate Forms
The doctrine of separate, universal Forms fails to explain the beings here and now. If Forms are apart from particulars, they cannot be causes of motion or of the “what-it-is” in individuals without multiplying entities needlessly. Moreover, a universal cannot be a substance. Form must be in the thing as its organizing principle, not a separate duplicate. Mathematics and universals have reality as abstractions, but not as independent substances.

First Philosophy and the Unmoved Mover
Beyond sensible, perishable substances and the everlasting celestial substances, there must be a highest, immovable substance that is pure actuality. Eternal motion requires an eternal, unmoved mover that causes as final cause, being loved and thought rather than pushing. This first principle is immaterial intellect, “thought thinking itself,” whose life is the highest activity. Theology thus becomes a part of first philosophy, since the first cause is a living, intelligible actuality that makes an ordered cosmos intelligible.