What Natural Bodies Are

A Theory of the Existence of Natural Bodies in terms of Forms

The word nature derives from the Latin natura, which was a standard translation of the Greek noun φύσις.

The Latin physica transliterates the adjective φυσική. This Greek adjective was used substantively (in place of a noun).

In the phrase 'inquiry into nature,' the Greek for 'inquiry' is ἱστορία. This Greek word transliterates as historia.

The title of Herodotus' Histories is Ἱστορίαι.

"This is the display of the inquiry (ἱστορίης) of Herodotus of Halicarnassus, so that things done by man not be forgotten in time, and that great and marvelous deeds, some displayed by the Hellenes, some by the barbarians, not lose their glory, including among others what was the cause of their waging war on each other" (Histories I.1).

The term 'natural history' preserves some of the ancient sense of 'inquiry into nature' (ἱστορία περὶ φύσεως). This is due in part to the importance in the history of science of Aristotle's Περὶ Τὰ Ζῷα Ἱστορίαι ("Inquiries about Animals"), which is commonly called by its Latin title Historia Animālium or English translation History of Animals.


Book II of the Physics:

Chapter 1. The nature in a thing
Chapter 2. The physicist
Chapter 3. Causes.
Chapter 4. Outcomes by luck and by accident
Chapter 5. Luck
Chapter 6. Accident
Chapter 7. Summary thus far
Chapter 8. The for something
Chapter 9. Necessity


"Of things that exist, some exist by nature (φύσει), some from other causes. By nature the animals and their parts exist, and the plants and the simple bodies (earth, fire, air, water)—for we say that these and the like exist by nature. All the things mentioned present a feature in which they differ from things which are not constituted by nature. Each of them has within itself a starting-point of change and staying unchanged .... For nature is a cause of being moved and of being at rest in that to which it belongs primarily, in virtue of itself..." (Physics II.1.192b).

"[One of the things] nature is said to be is the shape and form according to the account (ἡ μορφὴ καὶ τὸ εἶδος τὸ κατὰ τὸν λόγον)" (Physics II.1.193a).

"What is potentially flesh or bone has not yet its own nature, and does not exist by nature, until it receives the form according to the account (τὸ εἶδος τὸ κατὰ τὸν λόγον), which we name in defining what flesh or bone is. ... [So that in this way,] the nature of things having a starting point of motion is the shape or form, which is not separable except according to the account (οὐ χωριστὸν ὂν ἀλλ' ἢ κατὰ τὸν λόγον). ... And this is more [what] nature [is] than the material (ὕλης) [is]" (Physics II.1.193b).

"[T]he account and shape, which is individual and separable according to account (ὁ λόγος καὶ ἡ μορφή, ὃ τόδε τι ὂν τῷ λόγῳ χωριστόν ἐστιν)" (Metaphysics VIII.1042a).

"To what point should the physicist know the form and the what it is (τὸ εἶδος καὶ τὸ τί ἐστιν)? ... [To the point of] what is separable in form but in matter (ἅ ἐστι χωριστὰ μὲν εἴδει, ἐν ὕλῃ δέ) ... What is separable, and how things are with it, is a question for first philosophy to determine (πῶς δ᾿ ἔχει τὸ χωριστὸν καὶ τί ἐστι, φιλοσοφίας τῆς πρώτης διορίσαι ἔργον)" (Physics II.2.194b).
Aristotle thinks that each natural body has a "nature" (φύσις) and that this nature is the "starting point of change and staying unchanged." The nature, in this way, is what unites the differences in the history of a natural body so that these differences are changes in the history of one object. In the absence of the nature, there is only a heap of material.

Natures are Forms in Matter



Theseus slays the Minotaur. Theseus slays the minotaur

In the Phaedo, Echecrates asks why Socrates spent so much time in jail after his conviction. Phaedo answers that the execution was delayed because the ship of Theseus had not returned from Delos. The city had to be kept pure until the ship returned, so no executions were carried out.

Delos (Δήλος) is an island in the Aegean Sea. .
To understand what a "nature" is, Aristotle considers the prior two philosophical traditions. The Presocratic tradition after Parmenides eliminates ordinary natural bodies. Democritus, for example, conceives of the natural bodies in the traditional conception of reality as a "bastard" way of thinking about atoms in the void. Just how Plato understood natural bodies is not completely clear, but he seems to think that natural bodies exist in terms of forms.

Aristotle rejects the eliminativism in this Presocratic tradition. He thinks natural bodies exist, and he follows Plato in thinking that the existence of of natural bodies has to be understood in terms of forms. In the absence of the form, there is nothing more than a heap of material.

Aristotle understands the form as the organization of the material that makes the material be a natural body. He does not, however, think that of the existence of these forms in the way Plato thought. Aristotle is a Platonist, but he is also the first great Platonic critic. Aristotle thinks that these forms are not "separate." They are "in matter" and "separate in account."

The Existence of the Ship of Thesesus


"The ship on which Theseus sailed with the youths and returned in safety, the thirty-oared galley, was preserved by the Athenians down to the time of Demetrius Phalereus [fourth to third century BCE]. They took away the old timbers from time to time, and put new and sound ones in their places, so that the vessel became a standing illustration for the philosophers in the mooted question of growth, some declaring that it remained the same, others that it was not the same vessel" (Plutarch, Theseus 23).
The ship of Theseus provides an example to help show what Aristotle has in mind.

This ship was thought to be ancient by the time of Socrates' death and to have been repaired many times. If we ask what makes the ship that was repaired the same as the ship that first came into existence, its material does not seem to be the answer. The boards and other parts were replaced as the ship was repaired, but it is implausible to think that repairing the ship caused the unrepaired one to go out of existence and caused a new one to come into existence.

It seems that what makes the unrepaired and repaired ship the same is the organization of the material. This organization does not change in the course of the repairs to the ship. It is what persists and makes the ship of Theseus exist as one thing that is repaired over time.

Aristotle thinks that for natural bodies, just as for the ship, it is the organization of the material that constitutes identity. The identity consists in the way the material is organized. This organization makes the material be a natural body that can persist through change.

Aristotle's Theory of Forms

In this way, as the organization of the material, the forms of natural bodies are

• "in matter" and "separate in account."

By so describing these forms, Aristotle is explaining how the forms of natural bodies exist. They are "in matter" but also "separate" from the matter in a way. They are "separate in account." This makes them separate with qualification. The qualification is "in account."

To understand how the form is in matter and so not separate, consider again the ship of Theseus. The form is the organization of boards and other materials so that a ship of a certain kind exists. Removing this organization from the materials destroys the ship because without the organization, there is no ship. A pile of boards and other materials is all there is.

The form, however, according to Aristotle, is separate in a way. It is separate from the matter "in account." To understand what Aristotle seems to have in mind, consider a human being. The form is the organization of flesh, bone, and other materials, so that a human being exists. The account of the form in this case is what it is to be a human being. If, for Aristotle, this is rational animal, then the account (rational animal) makes no mention of flesh, bone, and other materials. This is how the form is separate from matter. It is separate in account.

This "separateness in account" is a little puzzling, but Aristotle's theory of the forms of natural bodies is relatively clear in outline. They are numerically distinct objects that are identical in account. Each is a numerically distinct organization of material, but because each organization makes the material be a body of the same kind, these organizations are identical in account. In the case of human beings, each organization makes the material be a rational animal.

"[Y]our matter and form and moving cause are different from mine, but they are the same in account according to the universal" (Metaphysics XII.5.1071a).




Perseus Digital Library:

Aristotle, Metaphysics
A Dictionary of Greek and Roman Antiquities: THEO´RIS (θεωρίς), THEO´RI (θεωροί)

Henry George Liddell, Robert Scott, A Greek-English Lexicon:
θεωρία, theōria, noun, "a sending of θεωροί or state-ambassadors to the oracles or games, or, collectively, the θεωροί themselves, the embassy, the mission"
θεωρίς, theōris, noun, "sacred ship, which carried the θεωροί to their destination"
θεωρός, theōros, noun, "envoy," ("spectator" in the sense of "overseer")

The θεωροί ("overseers") were sacred ambassadors or delegates sent on special missions (θεωρίαι) to perform some religious duty for the state, to consult an oracle, or to represent the state at some religious festival. In Athens, it seems that three ships carried the θεωροί: the Delia (Δηλία), the Salaminia (Σαλαμινία), and the Paralus (Πάραλος).) It seems that the Greeks thought that the Δηλία was very old and that it had once taken Theseus to Crete.

Arizona State University Library: Loeb Classical Library.
Aristotle, Physics




"Aristotle thinks that the capacity of an object to behave in this characteristic way [the way that characterizes it as a member of a natural kind] depends on its organization, structure, and disposition, indeed, he thinks that it is just this disposition or organization that enables the object to behave the way it does. Now, for Aristotle, the form is this disposition or organization, while the matter is what is thus disposed or organized" (Michael Frede, "Individuals in Aristotle," 66. Essays in Ancient Philosophy, 49-71).

"An important requirement was that the substance was to explain why, despite all the changes an object had undergone, it still is the same object. How the form could satisfy this requirement, we can see from the ancient example, expanded by Hobbes, of Theseus' ships, Theoris, which for centuries has been sent to Delos on an annual pilgrimage and whose return Socrates, in the Phaedo, must await before he may drink the poison. Over the years, the ship is repaired, plank by plank, always, however, according to the original plan. Now, let us suppose there is a shipwright who keeps the old planks. After all the old planks have been replaced in Theoris, he puts them together again according to the original plan and thus has a second ship. It seems obvious to me that this ship, even though it is constructed from all the old planks and according to the original plan, is not the old ship, Theoris, but a new ship; the ship constructed from the new planks is, in fact, the old ship. No insurance company, presented with a policy written for Theoris, would pay for damages suffered if the ship constructed from the old planks had been ship-wrecked. ... What makes for the identity of the repaired ship with the original ship is obviously a certain continuity. This is not the continuity of matter, or of properties, but the continuity of the organization of changing matter, an organization which enables the object to function as a ship, to exhibit the behavior of a ship" (Michael Frede, "Individuals in Aristotle," 66. Essays in Ancient Philosophy, 49-71).




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