## PhysicsBeta (B): What is "nature" (physis), or what does 'nature' mean?

Chapter 1. a. Some things exist "by nature", and some by other causes (aitiai, reasons). (This is not to say that those other things have nothing to do with "nature".)(See (d.) below for two senses of 'nature'.)

Examples: The wood in a bed exists "by nature", but the bed (as bed) does not; the bed was composed - was made to be a bed - not by nature but by art (techne). A person is a human, exists as a human, by nature; but he or she is a mechanic, or a parent, by choice and/or training.

b. What then is supposed to be the difference between that which exists, or is said to exist, by nature, and that which does not exist by nature, or that which is said not to exist by nature?--->All things existing by nature appear to have in themselves (whatever that means) a principle of motion and a principle of standstill.<--- (See Book Gamma on what motion, or a motion, is supposed to be.) What exists by art has a tendency for motion or change and for standstill only in so far as it happens to be made of something that exists by nature.
Examples: Suppose that a wooden bed happens to fall out of a 10th-story window. The bed breaks not because it is a bed, but because it is made of wood, etc., in a certain shape. Suppose that the person who is a mechanic and a parent hears of this incident involving the bed and becomes worried that his or her children might have been nearby when it happened. The person becomes worried not because of his or her skill as a mechanic (although that would certainly contribute to a human's awareness of the what could happen when a heavy object falls from a great height and smashes), nor because of the fact that he or she has children (although of course that would certainly give a person something to worry about) -- but because the person is a human. That is, dogs and cats who have offspring and who become aware of falling beds do not become worried about their young unless they know that the young were in the area of the falling bed. Gerbils who have offspring frequently do not protect them at all. The point is not that being a parent or a mechanic will not make a person react differently from one who is not a parent or a mechanic; certainly it can. The point, though, is that the principle (origin, source; arche) of the fact that one has certain reactions at all is that one is a human. Other animals may have, or seem to have, similar reactions; and they have them because of what they are by nature, i.e., because of whatever kind of animals they are.

c. --->Nature is a principle (arche) and a cause (aitia) of being moved, or of rest, in (whatever 'in' means) the thing to which it belongs primarily and in virtue of that thing, but not accidentally.<---
--->Whatever has such a principle is said to have a nature.<---
--->These things and whatever essentially (i.e. as part of their being what they are) belongs to them are said to exist "according to nature".<---
Example. When the bed fell out of the window, several factors were likely to have been involved: someone or something must have moved it to the window; perhaps the fall was planned; the window had to be able to be opened or broken; etc. But let us focus on the fall itself ("nature" was called "a" cause and "a" principle, not "the" cause, etc.). The bed was able to be moved because it was wooden, and not inextricably stuck to the floor; it fell (it did not rise, or stay suspended in mid-air) because it was (as wood) heavier than air and not propelled upwards by anything. The fact that it fell, and the fact that it broke into pieces on impact with the ground, were not due to its being a bed, or to its having a certain color.

"Nature", here, was then a principle and cause of the movement of the bed in so far as the bed was made of wood (or in general, of something heavier than air). "Nature" then belongs primarily to the wood, and is a cause and a principle (of the fall and breakage) in virtue of that wood, not in virtue of the fact that the fall involved a bed, nor in virtue of the fact that the bed was blue, nor in virtue of the fact that the fall occurred at 6:53 PM, etc. (The time of the fall, the exact color of the wood, and the way the wood was arranged would in this case be said to belong to the wood "accidentally", i.e. they are not part of what wood has to have, or has to be, in order to be wood.)

In that there does seem to be a principle (source; arche) that can move wood in virtue of the fact that the wood is wood, wood is said to "have a nature". (It would not be right to say that what we call "gravity" is the source, or the only source, of wood's movement. First, "nature" as source would in the case of wood include the source of wood's growth as well. Second, "nature" would include whatever it is about wood that enables it to be moved by gravity, growth, water, etc., cut by saws, and so on.)

Wood and everything that belongs to it in virtue of what it is (a certain chemical structure, a certain range of biological structures and functions, the fact that it is a solid and is visible, etc.) are then said to exist "according to nature".

d. Nature is "said" (i.e., we use the term "nature") in at least two ways or senses (193a30). In the first way or sense, it is said to be the first underlying matter in things which have in themselves a principle of motion or of change. In the second, it is said to be the shape or form according to formula.
1. "the first underlying matter...": 'Matter' (hule) means the stuff out of which something is made or composed. In this sense, if a thing can be moved or changed because of what it is, then whatever the thing is fundamentally made of or composed of will be called "nature" with respect to that thing, or will be called the "nature" of the thing.
2. "the shape or form...": 'Shape' (morphe) means shape, figure, configuration (usually visible). 'Form' (eidos) means form, kind, look (as in "I got my hair cut. Do you like my new look?"), appearance (visual or otherwise). 'According to formula' (kata ton logon) means according to the complete definition (or, total of defining characteristics) of a thing; according to the "formula" or account of a thing that presents the characteristics that the thing must have in order to be the thing it is. In this sense, "we call 'nature' that which exists by nature and is natural". How does this differ from the first sense? --Consider that even today, we say that wood does not exist in the form of planks "naturally"; what exists "by nature" and is "natural", we say, is trees. Moreover, while it is true that a seed, given water, light, and soil, may become a tree, we would not say that a seed (or seed+light+water+soil) "is" a tree, or that it "is by nature a tree", or even that it "has the same nature" as a tree (at least not in this second sense). That which is potentially flesh and bone (Aristotle's example), for example the things we eat that nourish our flesh and bones - or even the sperm and egg cells that have not united but will unite to begin the generation of a flesh-and-bone animal, is not (now) "by nature" flesh and bone. Hence that which is potentially flesh and bone (that which is said to "become" flesh and bone, or which will do so in future but has not yet done so) but does not actually now have the form of flesh and bone, is said not to have now the nature of flesh and bone. In this sense, then, we use the phrase "the nature of X" to refer to what has acquired the form by which we state what flesh or bone is.