cambCompChap5Science

Aristotelian Science: based on Hankinson's chapter 5 of CCTA

Infinite

to suppose that the infinite does not exist in any way at all leads clearly to many impossible results; time will have a beginning and an end, a magnitude will not be divisible into magnitudes, number will not be infinite. Physics 3.6 206a9ff.

Thus it seems Aristotle thought the infinite exists.
But he denies that there can be an actual infinity at 207b28.
He thought the world had no beginning, however.

Time and motion are indeed infinite, as is thought; but the parts that are taken do not persist. 208a20-21
The idea is that right now, there is no infinite time: each moment exists uniquely.

He also thought that the universe was finite in extent
and that it contained a finite amount of matter.
How did he solve these conundrums?
By introducing the notion of a potential infinity.

Actually infinite numbers do not exist, but potentially, numbers are infinite: you can always go further with numbers.
you cannot actually infinitely divide matter, but you can divide it again after every actual division: so it is potentially infinitely divisible even if you cannot actually infinitely divide it.

Why must the world be finite?

Because otherwise it would make no sense!
Start with the observation that earth and other heavy things go down.

Thus there is a "natural motion" for heavy objects.

But what of fire? It goes up. The more there is of it, the more it goes up.

If it had weight, the more there is of it, the heavier it would be, and so the more it would go down.
therefore, it has no weight: in fact, Aristotle thought that it had "lightness," which he conceived of as not just a lack of weight, but a positive presence of a quality contrary to heaviness. (cael. 3.1-2, 4.1-4) Cf. somewhat modern chemistry's 'phlogiston' which preceded the discovery of oxygen: it turned out to have negative weight!
And fire's natural motion is upward.
if the world were infinite, all the heavy stuff would go down, all the light stuff would go up, and there would be no mixture?

Motion

There are two kinds: rectilinear and curvilinear

Of rectilinear, there are two further kinds: up and down.

And so there are three "elements"

Fire (upward rectilinear)

Earth (downward rectilinear)

Ether (curvilinear)

Air and water he tried to work in as intermediate stages between earth and fire.

Earth has a natural motion downward toward the center (Aristotle thought the earth was the center): if the universe were infinite, there could be no center, but earth obviously moves downward, so there must be a center, and so the universe must not be infinite. If it's not infinite, it is finite!

Aristotle was wrong, obviously. So what?

First off, he uses empirical evidence: earth clearly does move down. The idea of gravity (force at a distance) was hard enough to accept later on: Aristotle was simply using what his senses told him.
Second, his theory is elegant: he uses a relatively small conceptual apparatus to explain a great deal.
admire him for that and forgive him his mistakes?

Dynamics

A given weight moves a given distance in a given time; a weight which is greater moves the same distance in less time, the times being inversely proportional to the weights... Furthermore, a finite weight travels any finite distance in a finite time. Cael 1.6 273b30-274a3

Proportionality!
a body of infinite weight must move at infinite velocity: weight gives it a natural motion downward.
but if you take a little away from that body, it should move at less speed.
Aristotle goes through this argument several times (Cael. 273b27ff, Phys. 233a32, )

Let A be the mover, B the thing moved, C the distance, D the time; then in the same time the same force A will move 1/2B twice the distance C, and in 1/2 D will move 1/2B the whole distance C--for thus the ratio will be preserved. Again, if a given force moves a given object a certain distance in a certain time and half the distance in half the time, half the motive power will move half the object the same distance in the same time.... But if E moves F a distance C in a time D, it does not necessarily follow that E can move twice F half the distance in the same time... in fact it may well cause no motion at all. ... otherwise one man might move a ship...Physics 7.5 249b29-250a16

Thresholds of movement: some things won't budge until you apply a certain amount of force to them: we explain it via friction. Aristotle knows nothing of friction.
BUT he does not deny the facts to preserve his theory!
He does not see any difference between an ant pulling a ship (a friction problem) and an ant lifting 1000 pounds (an acceleration problem).
BUT he does try to bring the phenomena under the umbrella of one mathematical explanation.

We see the same weight or body moving faster than another for two reasons, either because there is a difference in what it moves through... or because, other things being equal, the moving body differs from the other owing to excess of weight or lightness... A then will move through B in time C, and through D (which is less dense) in time E (if the size of B equals that of D) in proportion to the density of the impeding body. Physics 4.8 215a24-b4

Again, an attempt in simple terms to apply mathematics to explain dynamics

He notices that metal dust floats and that flat discs move through air differently than other shapes, but he does not figure out surface tension or aerodynamics.
In all, he is trying to be responsive to empirical facts while at the same time coming up with an elegant explanation.
if everything that moves is moved by something, how can some things which are not self-movers still continue to move when the mover is not in contact with them, such as projectiles? Physics 8.10 266b29-31

He cannot separate force from the substance which imparts the force. He thinks that an agent can only act on a thing while in contact with it. Hence he reduces all imparting of motion to pushing or pulling while in contact.
He has a problem with projectile motion:

he knows that it is a case of forced motion and so must end at some point.
but he does not know why the motion continues after the object that imparted the force is no longer in contact with the body in motion
His solution:

We must thus say that the first mover makes the air (or water, or whatever else can both move and be moved) such as to be able to cause motion, but that this does not cease to cause motion and to be moved at the same time, but stops being moved as soon as what moves it ceases moving, but still continues to cause motion, and so it moves something else consecutive with it. And the same thing is true for the latter. It stops in cases where the motive force engendered in the consecutive object is always less, and it comes to an end when the former can no longer make the latter a mover, but only moved. Cael. 3.2 301b18-30; Meteor. 368a7
so after the object is no longer in contact with the thing imparting force, that thing keeps imparting force to the medium in between, with decreasing effectiveness.
So some sorts of body have an ability to pass along force, such as air and water.

The structure of the world

The world is composed of concentric rings:

ether is the outermost ring

its natural motion is circular and infinite
form/matter distinction is not applicable there, because its denizens are immortal
this is basically Eudoxus' system: a mathematician in the Academy who worked out how to explain the erratic motion of planets via superimposed circles.

the next ring marks the separation of the sublunary sphere, the one we inhabit.

Meteorologica contains most of Aristotle's thoughts on this
four qualities in the sublunary sphere: cold/hot, dry/wet
four elements which combine the qualities: earth, air, fire, and water

these actually exist: the qualities do not exist in isolation
but what we usually call "earth" is not pure earth: it is already a combination of elements

the four qualities account for condensation/rarefaction, roughness/smootheness, heaviness/lightness, malleability, ductility, brittleness.

cold compacts things
heat can compact or rarefy them, depending on whether they are uniform or not.

interesting, because that means that he was not theorizing purely a priori: rather, he bent and twisted his theory to fit empirical observation.

Aristotle also makes a clear distinction between mere mixture and combination.
He only recognized two states of matter, solid and liquid, which caused problems for him.
He called some things "exhalations," which is sort of like gas.

So he reduces the phenomena to a simple set of explanatory factors: hence his explanation is "reductive"

we consider that we have given an adequate demonstrative account of things unavailable to sensation when our account is consistent with what is possible Meteor. 344a5-7

Interesting! "demonstrative"! so he thinks it is 'scientific' and 'proven'
phenomena need not be explained by the theory: rather they simply have to be compatible with it!

What does he explain in the Meteorologica in addition to elements, etc. above?

Aurora Borealis, Comets, Milky Way, rain, cloud, mist, dew, hoar-frost, snow, hail, winds, rivers, springs, climatic and coastal changes, source of saltiness of sea, earthquakes, volcanoes, thunder, lightning, hurricanes, haloes, rainbows, mock-suns.
everything which occurs naturally, but in a less orderly manner than that of the first element [ether] of bodies, in the place bordering most closely on that of the motion of the stars, e.g., the Milky Way, comets, meteors, everything we assign as being common attributes of air and water, as well as the kinds, parts, and attributes of the earth, from which we will examine the causes of winds and earthquakes, and whatever occurs as a result of their movements ..., as well as the fall of thunderbolts, typhoons, firewinds, and the other recurrent phenomena which occur to their bodies as a result of condensation. Meteor. 338b27-339a6
in other words, he is treating things that occur in the atmosphere or have to do with it somehow.
Comets:

he denied that they are planets (some effectively are and some ancients thought they were)
it would be hard for him to countenance irregularity in the ether sphere, so he must reject the idea that comets are there.

two spheres: the air and the fire sphere

not literally made of fire: rather it is flammable and catches fire from rubbing against the inmost ether sphere.

hence comets and meteors

not hot itself or made of fire
generates heat by friction

moved by force and so heats up
etc.

winds

exhalations from the earth

volcanoes

trapped exhalations from the earth: they explode out

source of all water

it is stable, unlike rivers

surounds earth, but not everywhere
the sun draws up the sweet part of it every day leaving the heavier part
then the sweet part condenses and falls back into it
regulated
the salt comes from dry exhalations which are by nature salty (residues are salty, don't you know?): it mixes with the moist in the clouds and then falls down salty and incrementally adds to the saltiness of the sea

that saltiness consists of a mixture of something is clear not only from what has been said, but also [from the fact that] if someone places a jar made of wax in the sea, having bound its mouth so as to prevent the sea getting in, the water which percolates through the wax walls becomes fresh: for the earthy part which causes the saltiness in the mixture is separated off as though by a filter. This is also the cause of its weight (for brine weighs more than fresh water), and of its density; for their densities vary so much that vessels laden with the same weight almost sink in rivers but ride well at sea and are seaworthy...An indication that the mass of a mixed substance is denser is that whenever one makes water highly salty by mixing salt with it, eggs will float on it. Meteor. 358b34-359a14
Two possible experiments! One false, one true.

Biology

Deer are the only animals in which the horns are solid throughout, and are also the only animals to shed them, on the one hand for the sake of the advantage gained by the increased lightness, but on the other hand from necessity because of their weight. de Partibus Animalium 663b12-15
Horns, teeth, and claws are required for defence: those animals with more toes (hence more claws) don't have horns. Only large animals have horns: because they have a preponderance of the heavy earthy in them and it must out. It either comes out as horns or tusks, but not both. Horns are often defensive, but sometimes useless: they have a final cause and a material cause, and at times one predominates. Defense versus material excess of earthy.
He thought that female insects insert a part into the male! and said it was easily observable! How empirical could even his biology have been in that case?
Parthenogenesis!

in some cases, no male of the species had been found, and so he said it might be the case

Spontaneous generation!

anemones, sponges, grey mullet, eels, testaceans all are spontaneously generated!
he bases this on evidence: no trace of reproductivity in any of them.

eels develop reproductive organs after they migrate to the Sargasso sea (that's true, not what A. thought)

testicles do not generate sperm

recently castrated bulls can still impregnate cows

dismissed the idea that hyenas have both a vagina and a penis

but hey, hyenas do have peniform clitorises: the things you learn in your Aristotle class!

observed hen's eggs each day after laying: Historia Animalium 6.3, 561a6-562a20)

So what should we make of Aristotle as a "scientist"?
On the one hand, he had a retarding, pernicious influence on the development of science.
On the other, he was phenomenally active and observed many things accurately and had many impressive and worthwhile insights into what science is.
Just as in logic, his detractors are unfair. The reason why he has a retarding effect was simply that he was so damned intelligent and active: it took a long time for enough people to be born who could question, improve on, or overturn his findings. That is not his fault.