Aristotle

by Various Works [lit]

  manifested in eternal phenomena; and there is hypothetical

  necessity, manifested in everything that is generated by nature as

  in everything that is produced by art, be it a house or what it may.

  For if a house or other such final object is to be realized, it is

  necessary that such and such material shall exist; and it is necessary

  that first this then that shall be produced, and first this and then

  that set in motion, and so on in continuous succession, until the

  end and final result is reached, for the sake of which each prior

  thing is produced and exists. As with these productions of art, so

  also is it with the productions of nature. The mode of necessity,

  however, and the mode of ratiocination are different in natural

  science from what they are in the theoretical sciences; of which we

  have spoken elsewhere. For in the latter the starting-point is that

  which is; in the former that which is to be. For it is that which is

  yet to be-health, let us say, or a man-that, owing to its being of

  such and such characters, necessitates the pre-existence or previous

  production of this and that antecedent; and not this or that

  antecedent which, because it exists or has been generated, makes it

  necessary that health or a man is in, or shall come into, existence.

  Nor is it possible to track back the series of necessary antecedents

  to a starting-point, of which you can say that, existing itself from

  eternity, it has determined their existence as its consequent. These

  however again, are matters that have been dealt with in another

  treatise. There too it was stated in what cases absolute and

  hypothetical necessity exist; in what cases also the proposition

  expressing hypothetical necessity is simply convertible, and what

  cause it is that determines this convertibility.

  Another matter which must not be passed over without consideration

  is, whether the proper subject of our exposition is that with which

  the ancient writers concerned themselves, namely, what is the

  process of formation of each animal; or whether it is not rather, what

  are the characters of a given creature when formed. For there is no

  small difference between these two views. The best course appears to

  be that we should follow the method already mentioned, and begin

  with the phenomena presented by each group of animals, and, when

  this is done, proceed afterwards to state the causes of those

  phenomena, and to deal with their evolution. For elsewhere, as for

  instance in house building, this is the true sequence. The plan of the

  house, or the house, has this and that form; and because it has this

  and that form, therefore is its construction carried out in this or

  that manner. For the process of evolution is for the sake of the thing

  Anally evolved, and not this for the sake of the process.

  Empedocles, then, was in error when he said that many of the

  characters presented by animals were merely the results of

  incidental occurrences during their development; for instance, that

  the backbone was divided as it is into vertebrae, because it

  happened to be broken owing to the contorted position of the foetus in

  the womb. In so saying he overlooked the fact that propagation implies

  a creative seed endowed with certain formative properties. Secondly,

  he neglected another fact, namely, that the parent animal

  pre-exists, not only in idea, but actually in time. For man is

  generated from man; and thus it is the possession of certain

  characters by the parent that determines the development of like

  characters in the child. The same statement holds good also for the

  operations of art, and even for those which are apparently

  spontaneous. For the same result as is produced by art may occur

  spontaneously. Spontaneity, for instance, may bring about the

  restoration of health. The products of art, however, require the

  pre-existence of an efficient cause homogeneous with themselves,

  such as the statuary's art, which must necessarily precede the statue;

  for this cannot possibly be produced spontaneously. Art indeed

  consists in the conception of the result to be produced before its

  realization in the material. As with spontaneity, so with chance;

  for this also produces the same result as art, and by the same

  process.

  The fittest mode, then, of treatment is to say, a man has such and

  such parts, because the conception of a man includes their presence,

  and because they are necessary conditions of his existence, or, if

  we cannot quite say this, which would be best of all, then the next

  thing to it, namely, that it is either quite impossible for him to

  exist without them, or, at any rate, that it is better for him that

  they should be there; and their existence involves the existence of

  other antecedents. Thus we should say, because man is an animal with

  such and such characters, therefore is the process of his

  development necessarily such as it is; and therefore is it

  accomplished in such and such an order, this part being formed

  first, that next, and so on in succession; and after a like fashion

  should we explain the evolution of all other works of nature.

  Now that with which the ancient writers, who first philosophized

  about Nature, busied themselves, was the material principle and the

  material cause. They inquired what this is, and what its character;

  how the universe is generated out of it, and by what motor

  influence, whether, for instance, by antagonism or friendship, whether

  by intelligence or spontaneous action, the substratum of matter

  being assumed to have certain inseparable properties; fire, for

  instance, to have a hot nature, earth a cold one; the former to be

  light, the latter heavy. For even the genesis of the universe is

  thus explained by them. After a like fashion do they deal also with

  the development of plants and of animals. They say, for instance, that

  the water contained in the body causes by its currents the formation

  of the stomach and the other receptacles of food or of excretion;

  and that the breath by its passage breaks open the outlets of the

  nostrils; air and water being the materials of which bodies are

  made; for all represent nature as composed of such or similar

  substances.

  But if men and animals and their several parts are natural

  phenomena, then the natural philosopher must take into consideration

  not merely the ultimate substances of which they are made, but also

  flesh, bone, blood, and all other homogeneous parts; not only these,

  but also the heterogeneous parts, such as face, hand, foot; and must

  examine how each of these comes to be what it is, and in virtue of

  what force. For to say what are the ultimate substances out of which

  an animal is formed, to state, for instance, that it is made of fire

  or earth, is no more sufficient than would be a similar account in the

  case of a couch or the like. For we should not be content with

  saying that the couch was made of bronze or wood or whatever it

  might be, but should try to describe its design or mode of composition

  in p
reference to the material; or, if we did deal with the material,

  it would at any rate be with the concretion of material and form.

  For a couch is such and such a form embodied in this or that matter,

  or such and such a matter with this or that form; so that its shape

  and structure must be included in our description. For the formal

  nature is of greater importance than the material nature.

  Does, then, configuration and colour constitute the essence of the

  various animals and of their several parts? For if so, what Democritus

  says will be strictly correct. For such appears to have been his

  notion. At any rate he says that it is evident to every one what

  form it is that makes the man, seeing that he is recognizable by his

  shape and colour. And yet a dead body has exactly the same

  configuration as a living one; but for all that is not a man. So

  also no hand of bronze or wood or constituted in any but the

  appropriate way can possibly be a hand in more than name. For like a

  physician in a painting, or like a flute in a sculpture, in spite of

  its name it will be unable to do the office which that name implies.

  Precisely in the same way no part of a dead body, such I mean as its

  eye or its hand, is really an eye or a hand. To say, then, that

  shape and colour constitute the animal is an inadequate statement, and

  is much the same as if a woodcarver were to insist that the hand he

  had cut out was really a hand. Yet the physiologists, when they give

  an account of the development and causes of the animal form, speak

  very much like such a craftsman. What, however, I would ask, are the

  forces by which the hand or the body was fashioned into its shape? The

  woodcarver will perhaps say, by the axe or the auger; the

  physiologist, by air and by earth. Of these two answers the

  artificer's is the better, but it is nevertheless insufficient. For it

  is not enough for him to say that by the stroke of his tool this

  part was formed into a concavity, that into a flat surface; but he

  must state the reasons why he struck his blow in such a way as to

  effect this, and what his final object was; namely, that the piece

  of wood should develop eventually into this or that shape. It is

  plain, then, that the teaching of the old physiologists is inadequate,

  and that the true method is to state what the definitive characters

  are that distinguish the animal as a whole; to explain what it is both

  in substance and in form, and to deal after the same fashion with

  its several organs; in fact, to proceed in exactly the same way as

  we should do, were we giving a complete description of a couch.

  If now this something that constitutes the form of the living

  being be the soul, or part of the soul, or something that without

  the soul cannot exist; as would seem to be the case, seeing at any

  rate that when the soul departs, what is left is no longer a living

  animal, and that none of the parts remain what they were before,

  excepting in mere configuration, like the animals that in the fable

  are turned into stone; if, I say, this be so, then it will come within

  the province of the natural philosopher to inform himself concerning

  the soul, and to treat of it, either in its entirety, or, at any rate,

  of that part of it which constitutes the essential character of an

  animal; and it will be his duty to say what this soul or this part

  of a soul is; and to discuss the attributes that attach to this

  essential character, especially as nature is spoken of in two

  senses, and the nature of a thing is either its matter or its essence;

  nature as essence including both the motor cause and the final

  cause. Now it is in the latter of these two senses that either the

  whole soul or some part of it constitutes the nature of an animal; and

  inasmuch as it is the presence of the soul that enables matter to

  constitute the animal nature, much more than it is the presence of

  matter which so enables the soul, the inquirer into nature is bound on

  every ground to treat of the soul rather than of the matter. For

  though the wood of which they are made constitutes the couch and the

  tripod, it only does so because it is capable of receiving such and

  such a form.

  What has been said suggests the question, whether it is the whole

  soul or only some part of it, the consideration of which comes

  within the province of natural science. Now if it be of the whole soul

  that this should treat, then there is no place for any other

  philosophy beside it. For as it belongs in all cases to one and the

  same science to deal with correlated subjects-one and the same

  science, for instance, deals with sensation and with the objects of

  sense-and as therefore the intelligent soul and the objects of

  intellect, being correlated, must belong to one and the same

  science, it follows that natural science will have to include the

  whole universe in its province. But perhaps it is not the whole

  soul, nor all its parts collectively, that constitutes the source of

  motion; but there may be one part, identical with that in plants,

  which is the source of growth, another, namely the sensory part, which

  is the source of change of quality, while still another, and this

  not the intellectual part, is the source of locomotion. I say not

  the intellectual part; for other animals than man have the power of

  locomotion, but in none but him is there intellect. Thus then it is

  plain that it is not of the whole soul that we have to treat. For it

  is not the whole soul that constitutes the animal nature, but only

  some part or parts of it. Moreover, it is impossible that any

  abstraction can form a subject of natural science, seeing that

  everything that Nature makes is means to an end. For just as human

  creations are the products of art, so living objects are manifest in

  the products of an analogous cause or principle, not external but

  internal, derived like the hot and the cold from the environing

  universe. And that the heaven, if it had an origin, was evolved and is

  maintained by such a cause, there is therefore even more reason to

  believe, than that mortal animals so originated. For order and

  definiteness are much more plainly manifest in the celestial bodies

  than in our own frame; while change and chance are characteristic of

  the perishable things of earth. Yet there are some who, while they

  allow that every animal exists and was generated by nature,

  nevertheless hold that the heaven was constructed to be what it is

  by chance and spontaneity; the heaven, in which not the faintest

  sign of haphazard or of disorder is discernible! Again, whenever there

  is plainly some final end, to which a motion tends should nothing

  stand in the way, we always say that such final end is the aim or

  purpose of the motion; and from this it is evident that there must

  be a something or other really existing, corresponding to what we call

  by the name of Nature. For a given germ does not give rise to any

  chance living being, nor spring from any chance one; but each germ

  springs from a definite parent and gives rise to a definite progen
y.

  And thus it is the germ that is the ruling influence and fabricator of

  the offspring. For these it is by nature, the offspring being at any

  rate that which in nature will spring from it. At the same time the

  offspring is anterior to the germ; for germ and perfected progeny

  are related as the developmental process and the result. Anterior,

  however, to both germ and product is the organism from which the

  germ was derived. For every germ implies two organisms, the parent and

  the progeny. For germ or seed is both the seed of the organism from

  which it came, of the horse, for instance, from which it was

  derived, and the seed of the organism that will eventually arise

  from it, of the mule, for example, which is developed from the seed of

  the horse. The same seed then is the seed both of the horse and of the

  mule, though in different ways as here set forth. Moreover, the seed

  is potentially that which will spring from it, and the relation of

  potentiality to actuality we know.

  There are then two causes, namely, necessity and the final end.

  For many things are produced, simply as the results of necessity. It

  may, however, be asked, of what mode of necessity are we speaking when

  we say this. For it can be of neither of those two modes which are set

  forth in the philosophical treatises. There is, however, the third

  mode, in such things at any rate as are generated. For instance, we

  say that food is necessary; because an animal cannot possibly do

  without it. This third mode is what may be called hypothetical

  necessity. Here is another example of it. If a piece of wood is to

  be split with an axe, the axe must of necessity be hard; and, if hard,

  must of necessity be made of bronze or iron. Now exactly in the same

  way the body, which like the axe is an instrument-for both the body as

  a whole and its several parts individually have definite operations

  for which they are made-just in the same way, I say, the body, if it

  is to do its work, must of necessity be of such and such a

  character, and made of such and such materials.

  It is plain then that there are two modes of causation, and that

  both of these must, so far as possible, be taken into account in