PHILOSOPHICAL DYNAMICS
CHANGE
[The material of this chapter can be found in Modes of the Finite, Part 2, Section 3, Chapters 1-3.]
Change is one of the most obvious facts we are confronted with; and it is one of the facts that science finds most interesting. And the reason why it is interesting to science is that change is the most obvious case of an effect, because the same thing becomes different while remaining the same.
Recognition of both sameness and difference are necessary for us to consider that something has changed; and this apparently contradictory situation always confronts us as needing an explanation.
First of all, it is obvious that there has to be a difference of some sort in order to say that a change has taken place. If the body (or anything at all) remains the same, this is another way of saying that it has not changed.
But at the same time, there cannot be total difference, or we would not be able to say that "something" changed. You might think that if you burned the book you are reading, then the ashes resulting are not "the same" as the book; but there has to be some sameness between them, because what happened was not that someone took away the book and put ashes where it was. These ashes were the book.
Actually, this is what the magician does when he asks you to believe that the silk hankerchief he put into the hat "turned into" the rabbit he pulls out. We didn't see the substitution take place, but we know that silk handkerchiefs do not become rabbits, and so we know that the one he put in there didn't change into one, and there was a replacement of the handkerchief by the rabbit. Of course, there was some change (of place) in both the handkerchief and the rabbit; but the point here is that in order to say that A changed to B, you have to be able to say that something about B is the same as something about A.
Hence, annihilation of something and creation of something else is not a change of the first into the second.
That is, if (supposing it to be possible) this book were suddenly totally to vanish and then a pile of ashes suddenly to come into absolute existence, this would be the same as the magician's trick with the rabbit. You might think that the book turned into ashes, but it didn't.
Annihilation or absolute creation cannot be considered changes, strictly speaking.
The reason for this is that if something simply goes out of existence, you can't, in a sense, talk about what happened to it (because there isn't any "it" any more--in any sense--to talk about); it didn't turn into anything; it just stopped. Similarly, if something absolutely comes into being, it didn't "come from" anything at all; it just began. Nothing changed into it--which does not mean that "nothingness" changed into it, but that "it is false to say that something changed into it."
This is perhaps not terribly significant except to clarify what we are talking about when we refer to a change: there must be (1) some difference, with (2) some continuity or sameness.
Given that a change needs something by which what changes can be identified as the same and also something by which it can be identified as different, then we can conclude the following:
Only BODIES (or systems of bodies) can change.
There are three things we need to investigate to reach this conclusion: God (the Infinite Activity), spirits (those acts not limited quantitatively), and bodies.
First, the only possible "change" God could undergo by which He could be any different would be to "become" something finite. If this were to happen, He would not change, but He and absolutely everything else would go out of existence; because anything finite is a contradiction unless it is being caused to exist as finite by the Infinite Activity. So, even if this were possible, it would not be a change.
Second, for a spirit to change, it would be necessary either for it to become a different kind of spirit, or for it to have a different property (supposing this to make sense). In the first instance, there would be nothing in common between the spirit that existed "before" and the one that exists "after" the "change, because there is only (a) existence and (b) the form of existence. But the existence can't be a "common element" enabling us to identify the second existence as "the same" as the first, because any two forms of existence can be called forms of existence. That is, existence is not a "common element" all activities share, as if it were a property; the form of existence simply means that the activities are of different kinds (it is not a "something" in addition to the existence). Thus, if the first spirit were annihilated and the second absolutely created, the second would still be a form of existence--and you couldn't say the first turned into the second. Hence, there is nothing in the spirit which would identify it in any sense as "the same" as the spirit before the change. So spirits can't become different kinds of spirits.
In the second instance, if the spirit acquires a new property (or loses an old one, the argument being the same), then even if spirits had real properties, the acquisition of a new property implies a difference in the spirit as a whole. But a "spirit as a whole" is precisely just a form of activity; and so any difference would mean a different form of activity--which is what we saw in the preceding paragraph could not happen. Hence, a spirit cannot change any of its properties.
Actually, spirits don't have properties in the true sense of the term, because the spiritual act, as I mentioned earlier, contains itself within itself; and so any "properties" would be one and the same act as the spirit. That is, any "ideas in the spirit's mind" would be identical with the whole spirit in reality, because each "idea" would contain within it (as conscious) every other "idea" the spirit had. But this is a complication that need not concern us except that it confirms that the spirit cannot be different in any way without being a different spirit; but in that case, it cannot change, because there is nothing to establish a continuity between "before" and "after." (Let me add that this does not mean that the spirit cannot-unchangingly-cause different, changing effects in something else, because, as we saw, the cause is not affected by its having an effect. This has to be true, because it can be proved that God cannot change, and of course, everything that is not God has God as its cause.)
Notice that you can't even replace a spirit with another one, since to be in a position means to be acted on to a certain degree by the fields of objects; but the spirit, not having a degree, can't be acted on to any degree--and hence is not in any position; and therefore, if he is annihilated and another spirit created, the second does not "take his place."
It therefore seems that you need the level of limitation of quantity in order for something to be able to change. If something becomes a different form of something, then the quantity before and after remains constant (which sounds suspiciousy like conservation of energy, doesn't it?); or if something becomes greater or less, then it is the same form of something that becomes greater or less.
Hence, it seems that change is a characteristic of energy or systems involving energy.
Note that we have not established that if something is a body it can change. All that we have been able to show so far is that if it is not a body, it can't change. It is at least conceivable that there could be unchangeable bodies.
Bodies are what change, then. Even when systems of bodies change, the bodies in the system must change somehow in order for the system to be any different. That is, the motions of the planets in the solar system seems at first glance to be something that is only going on between the planets, and in no sense within them; but this is only a superficial view. Insofar as the distances between planets vary, then they attract each other with different force, and hence the response to that force on the part of the planets will be different. Or, for instance, the drag of the moon on the rotation of the earth can be seen in the tides of the ocean. Hence, we can say that real changes in systems of bodies will imply changes in the bodies in the system; and so we need to look at how bodies can change.
There are two different sorts of changes bodies can undergo:
DEFINITION: A SUBSTANTIAL change occurs when the body becomes a different SUBSTANCE (i.e. KIND of body).
DEFINITION: An ACCIDENTAL change occurs when the body becomes different, but remains the same SUBSTANCE (i.e. KIND of body).
Note that this does not mean that a substantial change is a change of the "substance" (the unifying energy), and an accidental change is a change only in one or more "accidents" (properties). This was the oversimplification that some teachers taught in the late Middle Ages, and which was easily refuted by such philosophers as John Locke and David Hume.
No, an accidental change means that the body as a whole is different, but not that it is a different kind of body. Thus, when you blush, the new property you acquire (redness) means that you have been embarrassed, certain blood vessels have contracted and others (the ones on your cheeks) have dilated; your cheeks become hotter, your heart beats differently, etc., etc. The change takes place all through you, and you are different as a whole--which would have to be the case, since the property reveals the body as a whole.
Still, when you blush, you do not cease to be a human being. Thus, your substance, your kind of body, is still the same, though the body is different.
On the other hand, when a dog, say, dies, the corpse has many of the same properties (at least for a while) that the dog had; but the corpse of a dog is not the same substance as a dog; it is a different kind of body altogether, because the parts are no longer organized in a "doggy" kind of way, but behave more or less independently of one another. In fact, the corpse is now a system of various bodies, really, and not a single body any more; though it was a single body when it was a dog. So the death of a dog is a substantial change.
Note that certain interactions can be substantial changes from one point of view and accidental changes from another.
When you eat an egg, for instance, the egg ceases to be organized as an egg (the parts no longer interact in an "eggy" way), and the parts become assimilated into your body, and hence become parts of your body. The egg has undergone a substantial change, and has become you. So even though it isn't the case that "you are what you eat," it is true that what you eat is you (afterwards).
On the other hand, though you have gained some new parts and have increased your total energy-level, you are still a human being--the same substance you were before. So from your point of view, the change was accidental.
There is no contradiction here. If you ask what happened to the egg, the change was substantial; if you ask what happened to you, the change was accidental. There is no egg any more; there is just you--different from what you were, but not a different kind of thing.
7.3. Internal causes of change
It was sometimes taught that, just as in accidental change what remained constant was the "substance," so in substantial change what remained constant was the matter, and the "substantial" form was different. But in fact, with what we know now, this is a considerable oversimplification.
We can, however, make a reasonable description of what it is inside the body that allows for it to change--and in a given direction--if we take account of some of the properties of inanimate bodies we mentioned in the last chapter.
Inanimate bodies are controlled, as it were, by their matter, or by the amount of the energy unifying the body. This implies that a given form of unifying energy (at least in inanimate bodies) can only exist with a certain matter.
Let us define a couple of terms which will be useful:
DEFINITION: EQUILIBRIUM is the condition in which the form of the unifying energy of a body has the matter appropriate to it.
DEFINITION: INSTABILITY is the condition in which the form of the unifying energy has a matter that is incompatible with it.
That is, a body can only have a certain "shape" or configuration of its internal space (form of unifying energy) at a certain energy-level (matter). And this energy-level, as we saw, is the minimum amount of energy for this particular configuration of space.
If energy is added to the body and absorbed by it, then this distorts the internal configuration of the space, making it impossible for the body to exist as this kind of body at this energy-level.
That is, instability is an internal contradiction between the form of the unifying energy (which can only exist at a certain energy-level) and the matter (an energy-level different from the equilibrium level). But contradictions can't exist. Hence, the body cannot stay in the condition of instability.
[Note that instability is also this internal contradiction in living bodies also; but since they have a "biological equilibrium " above the ground-state, then they can be unstable either above or below this biological equilibrium-level. Inanimate bodies are unstable only above their equilibrium, since equilibrium is the lowest energy-state.]
I think we have to add that this distortion of the internal field creates a strain of some sort on the unifying energy and does not absolutely destroy it immediately. So that, even though the unstable condition implies an internal contradiction, it is not an absolute impossibility, and the body can be in the unstable condition, if only instantaneously.
The point, however, is that if a body is in an unstable condition, it immediately does something to get back into equilibrium. It changes, in other words.
Now there are two possible things the body can do: (a) it can restructure its internal field (the way the parts interact) so as to cope with this new energy-level, or (b) it can get rid of the excess energy and return to its ground-state.
If the body restructures itself, then it becomes a different kind of body (a different substance), and so we have a substantial change.
If the body returns to its ground-state, then the energy it gives off appears as a reactive property, and we have an accidental change.
Since inanimate bodies are controlled by their matter, then what the body is going to do and what its future equilibrium will be will depend on the amount of the excess energy introduced into it.
That is, inanimate bodies' changes are predictable if you know the amount of excess energy that makes up the instability.
For instance, if you take a test tube of mercuric oxide and hold it over a bunsen burner, the glass in the tube becomes hot, and the increased heat adds energy to the molecules of mercuric oxide (i.e. the faster-moving molecules of the glass hit the molecules of the mercuric oxide harder).
For a while, the molecules of mercuric oxide cope with this extra energy added to them (distorting their internal fields) by moving faster and hitting other molecules, transferring the excess energy to them (and making the whole system hotter).
But when a critical heat is reached, the molecule cannot by the elasticity of the forces inside it recover from the distortion, and it breaks apart, forming now atoms of mercury and oxygen (which, themselves unstable, form oxygen molecules).
So the first change as you heat the mercuric oxide is the accidental one which shows up as the reactive property of heat--and as you add more and more energy, the heat increases. But when the critical temperature is reached, the substantial change of becoming mercury and oxygen occurs. And you can tell when this restructuring of the internal space of the molecule will occur--if not by your theory of the "binding energy" (the unifying energy) of the molecule, then by observation at the temperature at which this happens. You will find that it always happens at just this temperature.
This theory of what happens in a change ought to be able to make some sense out of what physicists and chemists have observed in changes.
First, let us consider the law of "conservation of matter," which is now more generally formulated as the "conservation of mass-energy" (since in physics "matter" is not a technical term, and is almost but not quite equated with "mass," which ever since Einstein we know is not conserved.
What this law is actually saying is
In any change, the total QUANTITY of the energies involved remains constant, even if the forms of the energies differ.
This really is the "conservation of matter" in our sense of the term, if the matter (the quantity of unifying energy) is what controls what is going on in inanimate bodies.
Consider: if energy is introduced into a body, then the matter of the unifying energy is greater (the configuration of internal field is distorted because there is more energy in it than it can support). The body must then cope with this unstable condition.
If it changes accidentally, it does so by giving off the excess energy which it acquired, and falling back to its ground-state equilibrium. In this case, the amount of energy it gets rid of is the same as that which it absorbed when it became unstable. A new property is "acquired," but the total energy (original equilibrium + absorbed - emitted) remains the same.
If it changes substantially, it restructures itself in such a way as to be able to exist at this new energy level. In this case, the new substance(s) will obviously reflect the old equilibrium + the energy absorbed; and so the total energy will be the same.
Now of course, this body which has absorbed energy has to have got it from somewhere; and it would have got it either from "free energy" (if there really is such a thing), in which case, the amount it absorbed means that there is that much less "free energy" floating around; or it got it from some other body which is unstable (such as the Sun, for instance) and emitting energy by falling back to its ground state. If you take this energy into account (the energy given up by the causer) you will find that this is the energy absorbed by the affected object--and so the two are clearly equal, since they are the same energy.
Hence, no energy is lost in an absolute sense or gained. The matter (quantity of internal energy which indicates quantity of total energy) of the bodies in the system is conserved.
So this theory of change makes sense out of the first law of thermodynamics: that "energy is neither created nor destroyed"--and while it is at it, it shows the relation between this law and the conservation of matter, and why the conservation of "matter" in the naive sense of the old physics has to be reinterpreted as the conservation of the quantity of total energy.
If changes go from instability to some equilibrium, and if instability is (in inanimate bodies) an excess of internal energy, then this theory also explains the second law of thermodynamics: that the entropy of the universe always increases.
Let us look at what this law is saying. Basically, it says that whenever work is done (whenever energy is transferred from the causer to some affected object), the transfer is never a hundred per cent efficient; some energy is always wasted (and can be considered as heat given off--which is why this is a law of thermodynamics, the study of heat). This is one way of looking at the law.
Note that this does not mean that the energy wasted out of the bound state of the body or system goes out of existence. That would contradict the first law. No, what it says is that the energy is given off out of the system as "free energy."
In this sense, "entropy" is the tendency of energy to leave a "bound system" (a body or system of bodies) and be dissipated into the universe. Entropy is positive when the energy escapes the body and doesn't become bound in other bodies; it is negative if it is absorbed by a body from the surroundings.
Now then, if instability is an excess of energy inside a body, it follows that the equilibrium implied by this excess will be some lower energy-level of the body in question; and so some energy will be given off by that body as it goes from instability to equilibrium.
This will be true even in substantial changes, presumably, at least in inanimate bodies. The restructuring of the internal space of the unstable body or bodies will be such that the restructured space is "more efficient" than the unstable structure, and so the unstable body or bodies will "drop" into this new configuration, giving off energy.
Thus, a mixture of hydrogen and oxygen is in equilibrium because the internal energies of the hydrogen and oxygen molecules keep each other far enough apart so that they don't interfere with each other's space. But once some additional energy is introduced, forcing the molecules into each others' "territory," so to speak, a more efficient form of internal space becomes possible, and the molecules fuse together into water, giving off energy + an oxygen atom, which, moving faster, causes further disruption of the molecules near it, forcing others into this same new configuration; and the result is an explosion, with the whole system giving off a good deal of energy and becoming water (and possibly some excess oxygen, depending on the proportions of the original mixture).
Another way in which the second law of thermodynamics and entropy can be looked at is that the natural tendency of systems is toward randomness, not system. That is, energy tends to "unbind" itself rather than "bind" itself into bodies.
Obviously, there are cases where simpler systems (such as hydrogen and oxygen) combine naturally into more complex ones, when the total energy of the more complex system (or body) is less than the total energy of the (unstable) parts. But in this case, energy is given off, and so there is less energy left to bind things together.
And since this energy given off ultimately takes the form of heat, which is simply the random motion of parts of a body or parts of a system, then there is a kind of net increase in randomness even in these cases.
If, however, you are dealing with loosely knit systems, then this law says that if there is a non-random distribution of the elements to begin with, it will become random, and a random distribution will not systematize itself.
That is, if you drop a drop of ink into water, the ink will spread through the water until it is evenly distributed throughout. Inky water will not have the ink collect into a single area.
The reason for this seems to be that it takes more energy to keep the ink molecules all in the same place than for them to be batted any which way by whatever they come in contact with; and so water molecules will begin to invade the ink, and knock the ink farther and farther into the water. In order to collect the ink all into one place, you would have to work to keep the water molecules out of that area against their random tendency to go just anywhere. But this would take extra energy.
Hence, this is just a statistical way of stating that the tendency of any change is from a higher-energy to a lower-energy condition of the system changing.
And this in turn is another way of saying that in inanimate bodies, equilibrium is the lowest energy-state compatible with the configuration of the body in question, and instability is always a state of too much total energy--which is what our theory says.
[Note that funny things happen in thermodynamics when you consider living bodies (which spontaneously increase their total energy up till the point of "biological equilibrium" and then stay stable--in a sense--by losing and absorbing energy from then on). These are "open systems" in thermodynamic terms, where you have to consider the environment also in order to "close" the system and get the two laws above to work. That is, in order for these two laws of thermodynamics to be applicable to living bodies, you have to widen your perspective until the living bodies become parts of a basically non-living system of bodies. Then this whole system behaves according to the laws of physics. But the living parts of it don't really do so. Physicists tend to ignore this, because it implies that living systems are not simply fancy cases of inanimate systems, obeying the same laws--and so they invent terms like "open systems" to gloss over the contradiction between what is observed and what their laws (which apply only to inanimate bodies) say should be happening. Once you've put a name to something it looks as if you've nailed it down and explained it. You haven't.]
7.4. External causes of change
Aristotle called the "internal causes of change" matter and form, and in a sense the theory advanced here agrees with him. What Aristotle called "being in potency" I have called "being unstable," and only something that has a unifying energy (and so is a body or system of bodies) can be unstable, because instability is the discrepancy between the form of the unifying energy (or internal space of the body) and its matter (or strength of this internal field).
Aristotle considered matter to be "potency" to act (remember, he also thought of it as a kind of "stuff" which acted, not as limitation of the form of activity); but there is a difference between "potency" to be (any) form of activity and being in potency (to being some definite form of activity). He spoke of being "in potency" as a kind of "privation" or "lack" of some definite act. So, for instance, for Aristotle, matter could be an egg or a human being, say; but the matter of the egg would be "in potency" to being human when the egg was being eaten; it now somehow "had to be" the matter of a human being and nothing else.
Aristotle then considered the thing which was "in potency" to have an "end" or "purpose" outside itself; and it changed and got the "end inside itself" and existed in a rational way again, acting as it was capable of acting, and not being deprived of any form of activity.
Hence, Aristotle thought of the "purpose" (which didn't exist yet or was "outside" the "being in potency") to be one of the external causes of change. Every change would have a purpose (the form which was "lacking").
Thus, Aristotelian science was couched in terms of "purposes"; the form toward which a change headed was the purpose of the change. This has been downplayed in contemporary science, because the "purposiveness" got interpreted by the Christian commentators on Aristotle as what God wanted for the inanimate world--because you can only have a purpose when you know where you want to go, and obviously inanimate things can't know where they're headed--so God has to push them in the direction he wants them to go.
This was not at all what Aristotle had in mind; he was simply trying to account for the predictability of changes when conditions are basically the same. For Aristotle, this "purpose" which was just the (blind, mechanical) acquisition of the form that was "lacking" somehow was the primary notion of purpose, and human purpose (where you know what you want) is a notion derived from it (because you get headed somewhere).
In any case, I think our theory can show that Aristotle's notion of "purposiveness" is not foreign to modern science, but as a matter of fact is very heavily present in it; it explains the predictability of changes.
DEFINITION: The PURPOSE in any change is the EQUILIBRIUM implied in the instability.
That is, bodies change because they are unstable. Each instability, however, "heads itself" toward a predictable equilibrium, which is either the ground state (giving off the reactive property, in an accidental change) or a new structure (of a definite sort, in a substantial change). In inanimate bodies, we saw, this future equilibrium is predictable by knowing (a) the original equilibrium and (b) the amount of energy added to the body.
Now modern science is apt to ignore this, and say that the future state is predictable by knowing the energy acting on the body. That is, it's "what you do to it" that determines the future state, not some "purposiveness in the body itself."
But this is clearly contrary to fact.
For instance, if you take a mixture of hydrogen and oxygen, and you drop a lighted match (chemical energy) into it, you will get the explosion and water. If you pass a spark through it (electrical energy) you will get--the same explosion and water. If you compress it suddenly (mechanical energy) you will get the selfsame explosion and water; if you heat it up enough (heat energy) you will again get the explosion and water.
The point is, of course, that it makes no difference what the energy introduced into the body or system is, so long as it is the right amount.
Hence, it is the fact that the body is unstable to a particular degree which makes the results predictable, not what the energy was that got into it. That is, it is the internal distortion of the body which makes the new equilibrium predictable, not the form of the energy which distorted it; the distortion only depends on the amount of energy absorbed.
Hence, Aristotle's notion of "purpose" which was based on "being in potency" is actually a more accurate description of what is going on in scientifically predictable changes than the current scientific thinking which tends to shun "purposiveness." But modern science is right at least to this extent; "purposiveness" as we have defined it has nothing to do with somebody's MOTIVE for doing anything. It simply means that a given instability implies a given equilibrium, and if you know enough about the instability, you can predict the equilibrium.
With that said, we can resurrect the Aristotelian concept of purpose as scientifically useful; and we can add the following statements:
Only CHANGES have purposes. Equilibrium has no purpose.
This is obvious. Purpose is a future state, with its "seeds" somehow in the present; it is something that does not yet exist as such. But equilibrium exists; indeed, it IS existence in its most meaningful sense.
Something that "has a purpose" does not have (as Aristotle rightly noted) its full intelligibility in itself, but in some future condition of itself; it is not yet what it will be. But what is in equilibrium is completely what it is.
True, what is in equilibrium is finite, and hence is not completely self-explanatory; and so (as we briefly saw) needs God to account for its finiteness. But this is not the "incompleteness" we are talking about in instability, where the body is in a self-contradictory condition as it exists, and must exist in a different way or to a different degree.
A body in equilibrium depends on God, but is not headed toward God. This was the misinterpretation of "purpose" introduced by the Christians that has resulted in the whole concept's being thrown out by science. The body in equilibrium is stable, and intelligible as what it is (though finite); the body that is unstable is only intelligible through a future equilibrium.
Thus, not everything has a purpose; only changes (or, if you prefer, instabilities) do.
Secondly,
All changes have a definite purpose.
This would have to be the case. If the body is unstable, it cannot exist in this self-contradictory condition, and so must lose energy or reconfigure itself. Each of these would be a definite purpose.
Well, but couldn't it just keep changing? No, because (absent any new introduction of energy creating a new instability), there is only a finite amount of energy in the body, and if changing is from higher to lower energy, then it has to give off energy--and eventually it is going to run out of energy to get rid of.
Those apparent "changes" that are cyclic, where no energy is lost out of the system, are not changes but equilibrium.
Let me illustrate by the "perfect pendulum." If you start a pendulum going, and no energy leaves the system (by air resistance or friction), then the bob swings to the other side of its bottommost position exactly as far as it was on the first side; exactly all the kinetic energy is reabsorbed as potential energy, and it starts to swing back until it reaches its original position, where once again all the kinetic energy is potential energy, and this goes on forever. This would not be a change, but an internal activity of the system. The system is not unstable, as can be seen from the fact that it really never gets any different; it is simply active, not changing.
Now of course, no real pendulum is that way, because in fact when you pull the bob to one side (raising it up because of the rigidity of the arm), you have added energy to it. It then swings back, and (because of friction at the fulcrum and air resistance and so forth) it doesn't quite make it to the height it was when you let it go, and when it returns, it's a little lower still; and so on for each swing, until all the excess energy is removed, and it comes to rest at the bottom of the path of the swing. This loss of energy was the real change; the swinging was the way the pendulum lost energy.
And by the second law of thermodynamics, you can never add energy to a real pendulum (or any other system) raising it above its ground state without having it find a way to dissipate this excess energy.
Hence, any change will be headed toward a definite equilibrium--which it may not actually arrive at, if new energy is introduced before it gets there, creating a new instability--as when you wind a clock, making it give the pendulum a little push at every swing (restoring the excess energy and thus the instability).
In fact, the whole universe is headed toward a definite equilibrium: the "heat death" the astronomers talk about in the vastly far future, where all the stars will have burned out and there will be nothing but heat, with the temperature of space being raised some four or five degrees absolute.
Aristotle was right, then, in saying that you have to take into account the predictable future state (the purpose) if you want to make sense out of change. So we have three, so far, of Aristotle's "four causes" (form, matter, and purpose). And, like Aristotle, we can say that the purpose is a form, in a sense; that is, the predictable future state will involve some property (his "accidental form") or some new internal structure or form of unifying energy (his "substantial form").
The last of the "four causes" is the one everyone admits, and which has recently become synonymous with "cause." It is traditionally called the "efficient cause," and I see no need to change terminology here.
DEFINITION: The EFFICIENT CAUSE is the external energy which is introduced into a body, making it unstable.
This is the second of Aristotle's "external causes," and is obviously outside the body, since the energy level of the body is raised by it. Clearly, the body cannot give itself more energy than it has; and so in inanimate bodies, instability always implies an efficient cause.
[This is not necessarily so in living bodies, because their equilibrium is not their lowest energy-state; hence, if their energy drops below their "biological equilibrium" by natural processes, then this creates an instability without anything's being done to them from outside. Similarly, in those living bodies that have consciousness (which is not energy), the internal energy can be shuffled around by--for example--a choice, creating an instability in the body which was not there before the choice was made, and was not brought into being by any energy from outside. The choice itself can be made without any introduction of outside energy, because the choice is a spiritual act, without quantity. But this gets us into complications that are not part of this discussion. I mention in here, however, to show that, though inanimate bodies cannot act spontaneously (i.e. without being acted on by outside energy), living bodies and especially human bodies can act spontaneously.]
Note that the energy itself which is introduced into the body is the efficient cause; the body which gave off that energy is not the efficient cause, but the efficient causer. It has been a failure to make this distinction that has been the (logical) cause of a good deal of trouble in philosophy, and even sometimes in science.
Thus, if one billiard ball strikes another and makes it move, the first ball is the causer, not the cause of the movement. The kinetic energy of the first ball is the cause of the motion of the second one; because this is what was added to the second one (and subtracted from the first one), creating the instability in the second one which gave it the purpose of the property of movement and eventual rest somewhere else.
We say that the first ball "caused" the second one to move; and this is true; but it was the energy it imparted to the second one which was the cause of the movement; the first ball was the causeer, and has properties that had nothing to do with the movement.
Note that if the energy which is the efficient cause is energy given off by an unstable inanimate body which itself is seeking equilibrium, then the excess energy (the instability) of the causer needs an efficient cause. And since the energy of both the causer and the affected object is greater than before, the regress cannot be infinite. That is, if A's energy increases because B's energy is above equilibrium, then B got its increase from C, and so on; but you can't go on forever in this, because the combination A + B has more energy than equilibrium; and so does A + B + C, and A + B + C + D...; the whole system is in an unstable condition, with energy in excess of its equilibrium.
Hence, for any series of instabilities whose cause is energy given off by an unstable inanimate body, there must be a "first efficient cause" which is not an unstable inanimate body.
St. Thomas Aquinas used this as his "second way" for proving the existence of God; but unfortunately, it doesn't work. There are two possible explanations which don't need God. First, any one of these series can be stopped by an act of a living body (which can change spontaneously). Second, the whole universe might be like the "perfect pendulum" I mentioned above, and be in a state of "pulsating equilibrium," trading off energy between parts of itself and alternately expanding and contracting. Thus, the "big bang," the "first instability" which gives off the energy that starts the whole thing going, might be in fact the result of the collapse of the previous phase of the universe into the "fireball" which exploded.
If, of course, this unstable "fireball" can be shown not to be the result of a collapse of space (and this depends on the total amount of energy in space), then obviously the beginning of the universe as we know it is not self-explanatory; because an instability is a self-contradiction; and an unstable inanimate body (as the "fireball" would have to have been) would have to have an excess of energy which it couldn't have given itself. But if this is the whole of space, then there is no body it could have got this excess from.
It doesn't follow that this unstable "fireball" had then to have been caused by God, however. All that would be needed would be something that could raise the energy level of some kind of preexisting material into this instability. Granted, what this could be boggles the mind; but it wouldn't necessarily have to be (based on this effect alone) something infinite.
This, then, is what change looks like from the point of view of the body which changes. What about the act of change? This is the subject of the next chapter.