Natural Bodies, Natures, and Forms in Matter

The word nature comes from the Latin natura, which was a standard translation of φύσις (physis). The Greek for 'inquiry' in the phrase 'inquiry into nature' is ἱστορία. It transliterates as historia. (The title of Herodotus' Histories is Ἱστορίαι.) The term 'natural history' retains some of the ancient sense of "inquiry into nature." In large measure, this is due 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) and English translation (History of Animals).

"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 (ἀρχὴν ἔχει κινήσεως καὶ στάσεως).... 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.192b).

"[N]ature is said to be the shape or form according to the account (ἡ μορφὴ καὶ τὸ εἶδος τὸ κατὰ τὸν λόγον). ... 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, which we name in defining what flesh or bone is. ... [N]ature [said in this way] is the shape or form (not separable except according to the account (οὐ χωριστὸν ὂν ἀλλ' ἢ κατὰ τὸν λόγον) of things in them which is a starting point of motion. And this is more [what] nature [is] than the material (ὕλης) [is]" (Physics II.1.193a-b).

"To what point should the physicist know the form and the essence (τὸ εἶδος καὶ τὸ τί ἐστιν)? ... [To] that 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 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 no body. There is only a sequence of heaps 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 Crete. The city had to be kept pure until the ship returned, so no executions were carried out. .
To understand what a "nature" (φύσις) is, Aristotle considers the two prior two philosophical traditions. The Presocratic tradition after Parmenides eliminates ordinary natural bodies. Democritus, for example, the natural bodies in the traditional conception of reality are a "bastard" way of thinking about atoms in the void. Just how Plato understood natural bodies is not completely clear, but the idea is 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 that is "potentially" a natural body. The form is the organization of the material such that the material constitutes a natural body. These forms, however, do not exist in the way that Plato supposed. Aristotle is a Platonist, but he is also the first great Platonic critic. Aristotle thinks that the forms of natural bodies are "in matter" and "separate only according to the account."

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

What makes the original and the current ship the same over time is the organization of the material. This organization does not change in the course of repairs to the ship. The organization is what persists and makes the ship of Theseus be one thing that is repaired over time.

In the case of natural bodies, just as in the case of the ship of Theseus, it is not the material but is the organization of the material that constitutes identity over time. Their identity consist in the way this material is organized. This organization is what makes the material be a natural body.

Aristotle's Theory of Forms

Aristotle thinks that the forms of natural bodies are "in matter" and "separate only in account." By so describing these forms, he is making a point in ontology. He is explaining how the forms of natural bodies exist. They are 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 exists in and cannot be separated from the matter, consider the ship of Theseus. The form is a certain organization. It is the organization of boards and other materials so that a ship exists. Removing this organization from the materials destroys the ship because without the organization, a pile of boards and other materials is all that remains.

The form, however, according to Aristotle, is separate from the matter in a way. It is separate from matter "in account." To understand this, 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 is what it is to be a human being. If this is rational animal, then the account makes no mention of the flesh and bone. This is how the form is separate from matter. It is separate in account.

"The completed whole, such-and-such a form ( in this flesh and these bones, is Callias or Socrates. They are different because of the matter (for that is different), but they are the same in species; for the species is indivisible (ἄτομον)" (Metaphysics VII.8.1034a). "[T]he causes of things in the same species are different, not in species, but because the causes of the individuals are different: your matter and form and moving cause being different from mine, as they are the same in the formula according to the universal (τῷ καθόλου δὲ λόγῳ ταὐτά)" (Metaphysics XII.5.1071a).

Aristotle, in this way, thinks that the forms of natural bodies are numerically distinct but identical in account. Each is a numerically distinct organization of material, but because each organization makes the material be a natural 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.

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, "sending of θεωροί or state-ambassadors to the oracles or games, or, collectively, the θεωροί themselves, embassy, 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 sacred ambassadors or delegates ("overseers") 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 another land, where among other ceremonies sacrifice would be offered on behalf of their state. In Athens, there were three ships used to carry the θεωροί: the Delian (Δηλία), the Salaminian (Σαλαμινία), and the Paralus (Πάραλος).)

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

"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. Moreover, this would be so even if the planks had been changed all at once, not over many years; it would be even so if the ship constructed from the new planks were constructed according to a modified plan so that, perhaps, only the ship constructed from the old planks was constructed according to the original plan. 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, Michael Frede (University of Minnesota Press, 1987), 49-71). )

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