Summary: Metaphysics (page 5)

Book Δ

In this book, Aristotle defines several fundamental concepts.

For instance, the concept of principle: the primitive element that causes a thing to be, to occur, or to be known ¹. Thus, the principle of a child is its father and mother; the principle of a boat is the keel, and so on.

He also defines element: The primary and intrinsic part of a thing ².

Nature, meanwhile, is defined as the essential substance of beings that possess within themselves the principle of motion ³.

Book Ε

In this book, and in those that follow, Aristotle seeks to identify the essential characteristics of the science of being as being. The chief ones are as follows:

The traditional sciences neglect Being itself, focusing instead on a particular part of it: All the sciences [...] do not devote the slightest attention to Being taken in an absolute way; that is, they do not examine it as Being ⁴.

This is precisely the province of first philosophy.

Here, Aristotle introduces his famous tripartite division of the sciences:

Any application of thought is either practical, or productive, or theoretical ⁵.

Theoretical sciences include mathematics, physics, theology, and first philosophy.

Books Ζ and Η

The notion of being is plurivocal; the categories express its different meanings. However, substance is the primary meaning of Being.

Yet the notion of substance is itself manifold. It can be understood as essence, universal, genus, or subject.

Of these, the subject — the compound of matter and form — appears to be the most fundamental sense of substance.

Aristotle rejects the materialist doctrine that identifies substance solely with matter, treating everything else as mere modifications of it. He likewise rejects the opposite doctrine, which identifies substance exclusively with form: No universal nor genus is substance ⁶; rather, substance is subject and matter ⁷.

Book Θ

Being can exist as substance, in potency, or in act.

In this book, Aristotle defends the notion of potency against those who deny it — namely, the Megarians, who claim that only act is real.

A builder remains a builder in potency even when he is not actively building anything.

The Megarian position eliminates the very possibility of change by rejecting potency.

Yet act is prior to potency, and more fundamental: it is impossible, for instance, to be a lyre-player without having already played the lyre.

Thus, potency is intelligible only with reference to act: It is not in order to have sight that animals see; but, on the contrary, they have sight in order to see ⁸.

Book Κ

Here, Aristotle distinguishes between practical science, theoretical science, and productive science.

These sciences are distinguished by the nature of the objects they study.

In a theoretical science, such as physics, the principle of an object's movement lies within the object itself.

By contrast, in the other two types of science, motion originates with the acting or creating agent.

Book Λ

Every movement is caused by a preceding movement, which is itself the effect of an earlier one, and so on.

It is therefore necessary to conceive of a first movement imparted by a first mover — one that is itself immobile (for if it were moved, it would not be first) and, consequently, eternal.

Such a mover is necessary for another reason as well: If something is moved, it is because it can also be otherwise than it currently is. [...] But as long as there exists something that gives motion while itself remaining immobile and actual, that thing absolutely cannot be otherwise than it is ⁹.

Contingency, then, characterises everything except the first mover: Of necessity, this principle exists; as necessary, it is perfect as it exists; and it is on this account that it is the principle ¹⁰.

From this, Aristotle demonstrates the existence of an eternal, immovable substance — separate from all other beings accessible to the senses ¹¹.

Divine Intelligence thinks only of what is highest — and thus thinks of itself:

This Intelligence thinks of itself, since it is what is most perfect; and Intelligence is the intelligence of intelligence ¹².

By contemplating itself, this Intelligence possesses and subsists throughout all eternity ¹³.

¹ Book Δ, 1
² Δ, 3
³ Δ, 4
⁴ E, 1
⁵ E, 1
⁶ H, 1
⁷ H, 2
⁸ θ, 8
⁹ Λ, 7
¹⁰ ibid.
¹¹ Λ, 9
¹² Λ, 9
¹³ I,1, 402a