Saturday, July 9, 2011

Induction of Aristotle’s Theory of Four Causes

The aim of this essay is to retrace the steps Aristotle had to reach in order to induce his revolutionary theory of causality, second only to his theory of logic in philosophical importance. In presenting these steps, we’ll also see several philosophical problems he solved in the process of reaching his theory of four causes.

We’ll cover six steps, although his discovery could easily be broken up into many more:

1. Consider the opposing views of Parmenides and Heraclitus concerning change and in what respect Aristotle agreed with them, and disagreed.

2. Understand that Aristotle’s concepts of “potentiality” and “actuality” solve the metaphysical problem of change confronted by his predecessors.

3. Exploit Aristotle’s concepts of “form” and “matter” (among others) to understand what the process of change amounts to.

4. Grasp that any process of change requires a cause, an agent that can initiate the process, and an effect, a patient that receives the change.

5. Reach Aristotle’s conclusion that there are four kinds of causes that can explain any process of change and any fact, as well as consider some applications of the final theory.

6. Show how Aristotle’s account of causality handles (1) objections to final causality, and (2) the phenomena of spontaneity in nature, and chance in human events.

Parmenides, Heraclitus, and the Problem of Change

Heraclitus (c. 535–c. 475 BCE), a Pre-Socratic philosopher, is said to have believed that the universe is in an eternal flux, a constant process of changing. “We both step and do not step in the same rivers. We are and are not.” There are no real things; the processes are what really exist. The world consists of many processes, changing from one side to its opposite: war and peace, satiety and hunger, day and night, and even motion and rest, the process of change unites them all. “All things are one.” According to the Neo-Platonist Simplicius, “everything flows,” is the central philosophy of Heraclitus.

Parmenides (early 5th century BCE), another Pre-Socratic philosopher, held the opposite view of the universe: that it is stable and unchanging. Parmenides was probably the first person (and philosopher) to grasp the concept of “existence” as such, because he held that, “What is, is.” Logically, he reached the idea of nonexistence as well: what is not, is not. In his view, there were only two alternatives for anything: being and non-being. Correspondingly, there were only two inquiries for a person to conduct: to discover “that it is,” and “that it is not.” But the second inquiry will never work, because nothing cannot exist (cannot be a “thing,” a “being” to inquire about). (Italics added)

Parmenides endorsed several other conclusions as implications of his views on being and non-being. One conclusion was that nothing new (nothing that is) can come from non-being because “nothing comes from nothing.” Another was that being is eternal, it already is, and does not “begin” to be: "being cannot come from being since it is already."
(See “The Problem of Change”)

What Parmenides concluded from this is that there is no such thing as change, becoming, destruction, or even motion.

This led to what is known as the “Problem of Change”: “All change is change of something. There must be a thing that changes; and that thing must remain, while it changes, identical with itself. But if, we must ask, it remains identical with itself, how can it ever change?” [Karl Popper, “The World of Parmenides: Essays on the Presocratic Enlightenment,” p. 155]

Aristotle saw the merits of both sides on this issue. With Heraclitus, he agreed that change certainly exists, we’re aware of it every day. But he also agreed with Parmenides that “what is, is,” that stable things exist with definite identities (he termed them “substances,” like particular men, horses, carts). How was he able to combine and integrate these two views, such that we would have stability with change?

“Potentiality” and “Actuality” as the Solution to the Problem of Change

Aristotle improved upon the thinking of previous philosophers, and in particular upon Parmenides, by noting that “being” and “nonbeing” do not exhaust the field of what can be distinguished in Ontology (known as the field that studies “being” or existence as such, instead of other questions about existence, such as the study of God in Theology). “Being” can be further distinguished in Aristotle’s philosophy: we can compare “being-in-potency” with “being-in-act.”

He reached the concepts of “actuality” and “potentiality” from observing changes, in particular, changes to “accidental” features of a thing. “Accidental” refers to non-essential qualities of a thing, such as the shape of an instance of marble—whether it is a geometric block, or in the shape of a statue, it is still essentially marble, and its shape at any time is only an accidental feature.

A sleeping man is actually asleep, but is potentially awake; An oak tree is actually a tree, but potentially a wooden table (assuming the human tools and intentions are actual); a child is actually a child, but potentially a grown man. This can only happen because of a property within these actual things—the capacity to be transformed. These potencies or potentialities are inherent in the actual things: they are not “nothing,” and not “nonbeing.” (“The Problem of Change”)

It was a point known by many people before Aristotle, such as the Greek law students who knew they were potentially lawyers, but knew that they had to study to actualize their potency. But it was Aristotle who first grasped how the "potential"/"actual" distinction applied to “being” as such. He grasped that potentialities are part of the nature, i.e., identity, of actual things, and this is the way that stability and identity could be reconciled with change. Changes happen in accordance with the nature or identity of the thing that undergoes the change. For instance:
Nor again do things pass away into the first chance thing; white does not pass into musical (except, it may be, accidentally [e.g. a white man may turn into a yellow man due to the disease jaundice, and also become a musician]), but into non-white—and not into any chance thing which is not white, but into black or an intermediate; musical passes into not-musical—and not into any chance thing other than musical, but into unmusical or any intermediate state there may be. (Physics, book 1, chapter 5, 188b4, words in brackets are mine.)
For from the potentially existing the actually existing is always produced by an actually existing thing, e.g. man from man, musician by musician; there is always a first mover, and the mover already exists actually. We have said in our account of substance that everything that is produced is something produced from something and by something, and that the same in species as it. (ibid., book 9, chapter 8)
This is the means by which Aristotle solved one of the earliest philosophical problems in the field of Metaphysics.

Change as a Process of Matter Losing, and Taking on, Certain Forms

His solution raises some new questions, however. What are the elements involved in change as such? What are the kinds of changes that can occur?

Matter, Privation, and Form

Aristotle had observed many changes, and so he was able to generalize the three principles that explain the phenomenon of change:

1. The matter of a subject stays the same throughout the change.

2. Privation is something that passes away from the subject during the change, something that it had before the change started.

3. The form is something that comes to be in the subject as a result of the change, which it didn’t have prior to it.

Let’s say that a tailor is going to cut up and sew some cotton in order to make a shirt. In this process of change, the matter is the cotton, the substantial form and matter of cotton united, the privation is the formless shape of the cotton before the change, and the form is the finished shape of the cotton shirt.

Or we’ll take one of Aristotle’s examples of an “unmusical man”: through studying under an actual musician, the unmusical man becomes musical himself. The matter is the man, the privation is his unmusical quality, and the form is the result of the change, his musical form.

(Aristotle considered these points about matter, form, and privation to be a second answer to Parmenides’ concern about “being” and “nonbeing.” Parmenides treated “being” and “nonbeing” as simple phenomena, but Aristotle knew from his distinctions that a given thing is a “being” in a qualified sense, and a “non-being” also, in a qualified sense: an unmusical man comes to be a musician from a kind of “being” (being a man) and a kind of “nonbeing” (not being musical). “We ourselves are in agreement with them in holding that nothing can be said without qualification to come from what is not. [“Nothing comes from nothing.”] But nevertheless we maintain that a thing may 'come to be from what is not'-that is, in a qualified sense. For a thing comes to be from the privation, which in its own nature is not-being,-this not surviving as a constituent of the result.” (ibid., book 1, chapter 8) )

Aristotle viewed change as a subject’s potentiality becoming actualized. He saw it as a persisting subject (matter) losing something that it previously had (privation), and gaining something new as a result (form). “For man remains a man and is such even when he becomes musical, whereas what is not musical or is unmusical does not continue to exist…” (Physics, book 1, chapter 7)

Change as moving from one contrary state to another

Lastly, he viewed it as a process in which a subject moved from one contrary state to the other contrary, or an intermediate between the contraries: a white subject changes into a black one, or an intermediate between the two, like some kind of gray. (“Aristotle on Change”)
A house comes from certain things in a certain state of separation instead of conjunction [separation and conjunction being contraries of each other], a statue (or any other thing that has been shaped) from shapelessness-each of these objects being partly order and partly composition [meaning that order must come from something disordered, and composition from something unconstructed, or at least an intermediary between the two]. (Physics, book 1, chapter 5, words in brackets are mine.)
Accidental and Substantial Changes

From his observations, he distinguished between two kinds of change: accidental change and substantial change.

Substance is an important concept in Aristotle’s philosophy, similar to our concept of “entity.” A substance is something that can exist in its own right, and is not a property of something else. Man, horse, and chair are substances. Being white, musical, sturdy, or violent are not substances, but are “predicated of substances.” Qualities, quantities, states, positions, relations, actions, and being acted upon (“affections”) are all aspects of substances, and they are predicated of substances. In Aristotle’s view, substances are compounds of form and matter. Accidental and substantial changes are changes to substances, but in different ways.

An accidental change occurs when a substance undergoes a transformation of one of its qualities (a kind of motion he calls “alteration”), its size or quantity (“growth” and “diminution”), or a change in its place (“local motion”). Examples of accidental changes would be ripe bananas becoming rotten, a blade of grass growing longer, and a boy running across the street from one house to another. These accidental changes, or motions, are processes in which a substance loses one accidental form or actuality and gains another. In this case, the forms of the substance’s accidents change, but the substance itself—its substantial form and its matter—stay the same throughout the change.

Substantial change occurs when a substance either passes away, which is called “corruption,” or comes to be, which is known as “generation.” If I take a medication pill, it eventually stops being the substance “pill” and becomes a part of me, which is an example of corruption. (Paraphrased from “The Four Causes”.) An example of generation would be a woman giving birth to a baby, which is an instance of the substance “human” coming to be. The elements of a substantial change are similar to an accidental change—matter suffers the privation of the substantial form it once had, and this form is replaced by a new substantial form, and thus the unity of matter and form in a substance is preserved.

Change Requires an Agent and a Patient

The last element that we’re going to cover here is that Aristotle reached the idea that change requires an agent, something that is responsible for the change. This change will take place in a patient, something that is acted upon by some agent.

To reach that idea, Aristotle analyzed the relationship between “the mover,” and “the movable” (see Physics, book 3). “A thing is capable of causing motion because it can do this, it is a mover because it actually does it. But it is on the movable that it is capable of acting.” Aristotle’s idea is that the mover and the movable, or the agent and the patient, both share an interdependent relation with each other. A patient requires an agent to undergo a given motion or change, but an agent requires a patient on which it can act to realize the action.

An excellent example is that of the teacher and the student. A teacher cannot teach without someone present to learn, and the learner requires a teacher to learn. As Anna Marmodoro makes the point, “[t]eaching causes learning. Neither can happen without the other. The teacher is not teaching if the learner is not learning, and the learner (i.e. ‘instructee’) is not learning (being instructed) if the teacher is not teaching.”
(Anna Marmodoro, The Union of Cause and Effect in Aristotle: Physics 3.3, p. 23 of the PDF)

He also analyzes the relation between the agent and the patient with his ideas of potentiality and actuality. The agent, the teacher, has the potential to teach, and the patient, the instructee/learner, has the potential to learn. Both of these potentialities have the same actualization process, which actualizes both the potential of the teacher and that of the learner.

A conclusion he explicitly avoids is the thought that two potentialities can have the same actuality, because that would mean that teaching would be the same thing as learning (see Aristotle, Physics, 3.3); both teaching and learning undergo the same overall process (i.e. a sustained presentation of certain facts and reasoning about the facts), but teaching and learning differ in definition, just as agency and patiency do. Aristotle is making the point that teaching and learning have sameness with a qualification (i.e. only in certain respects, not absolute identity): they share the same process to actualize themselves, but are not the same in definition (see Marmodoro, p. 20 of the PDF).

Aristotle explains this point further:
But indeed it by no means follows from the fact that teaching is the same as learning, that to learn is the same as to teach, any more than it follows from the fact that there is one distance between two things which are at a distance from each other, that the two vectors AB and BA, are one and the same. To generalize, teaching is not the same as learning, or agency as patiency, in the full sense [that is, by definition], though they belong to the same subject, the motion; for the ‘actualization of X in Y’ and the ‘actualization of Y through the action of X’ differ in definition. (Physics, 3.3, words in brackets are mine.)
In this passage, we can begin to see why change requires an agent and a patient. Both are required for the motion to occur, for “the mover” to move or change “the movable.”

The essence of this process of motion or change is the carrying of a form from the mover to the movable, from the agent to the patient. “This mover will always [carry, be a vehicle for] a form, either a ‘this’ [substance] or such [quality] or so much [quantity], which, when it moves, will be the principle and cause of the motion; for example, the actual man begets man from what is potentially man.” (ibid., words in brackets are mine.)

This notion of some patient receiving a new form from an agent is Aristotle’s account of what it means to “cause” something. Causal efficacy is the capacity of an agent to carry a form to a patient, from the actual to the potential.

Aristotle’s Theory of Causality as Four Ways to Explain a Fact

The History and Development of the Theory

Aristotle states the rationale of his theory of four causes in the opening of Physics book 2, section 3:
Now that we have established these distinctions [on the meanings of “nature,” and between mathematicians and physicists], we must proceed to consider causes, their character and number. Knowledge is the object of our inquiry, and men do not think they know a thing till they have grasped the ‘why’ of (which is to grasp its primary cause). So clearly we too must do this as regards both coming to be and passing away and every kind of physical change, in order that, knowing their principles, we may try to refer to these principles each of our problems.
In Aristotle’s view, there may be four explanations or answers to the question “why?” for any fact or change. Suppose a person asked “why does this fork exist?” To that, Aristotle could answer in four ways. One way was that the fork exists because it is made out of silver, which would be the material cause. Another way to explain its existence is that it allows people to dine on food by poking it, which would be the formal cause. Yet another way is that it exists because silver was melted down and molded and shaped by processes and silverware-makers into a fork, which is the efficient cause, the source and the steps of change. And finally, one could say that the fork exists because a fork-maker had the purpose to create this fork so that people could use it to eat food, which is the final cause, or “that for the sake of which” a thing is done, as Aristotle calls it.

He developed this scientific account of causality by extrapolating from his own biological and artistic studies, and by studying the history of the idea of “cause” found in previous philosophers. (See Metaphysics, book 1, for Aristotle’s account of the history of “causation.”)

His philosophical predecessors, the pre-Socratics, Socrates, and Plato, originated the ideas of certain things being material causes. The philosopher Thales thought that water was the underlying principle or source of everything else; Heraclitus thought it was fire, which is always changing; Anaximenes and Diogenes held that air was the source of all things, and prior to them all, etc.

Aristotle also acknowledges that some of the Pre-Socratics investigated a second cause—the source of the process or change, or what makes a change occur: the efficient cause. Empedocles, for instance, held that “friendship” is the source of good things (i.e. things become good due to the quality of friendship), and “strife” is the source of bad things. Anaxagoras believed that rational laws made the world the way that it is. Aristotle realized that such an investigation was necessary because a search for only material causes was insufficient for truly understanding facts. His counter-argument to the idea of material causes being the only genuine cause was that, “the substratum itself does not make itself change; e.g. neither the wood nor the bronze causes the change of either of them, nor does the wood manufacture a bed and the bronze a statue, but something else is the cause of the change.” (Metaphysics, book 1, part 3)

The third cause, the final cause, was a new invention of Aristotle’s, and he notes that the philosophers before him conceived of some source of a change or efficient cause, but not the “[t]hat for whose sake actions and changes and movements take place.” He observed that those who held that reason or friendship were the start of changes (the efficient cause), didn’t also hold that things change or move for the sake of reason or friendship. (ibid, part 7)

The fourth and last cause, the formal cause, was adopted principally by his teacher, Plato, who theorized that the Forms or Ideas of things are the true reality, and that physical objects become real as they “participate” in one Form or another. The Form was the essential qualities or essence of something, and these essences are what caused other things that participate in or imitate it to exist (the Form of Man was the cause of individual men). Like Aristotle’s formal cause, the Form was what made things the kind of things they were.

All of these observations and thoughts, including his study of animals and nature, led to several wide-reaching inductions about cause-and-effect.

The material cause, “that out of which,” is the wood of a tree or table, a woman of the generation of a baby, the silver of a saucer, and the bronze of a statue. (He doesn’t just mean physical things though: letters are the material cause of syllables, and premises are the material cause of a conclusion, he remarks. See Physics, book 2, part 3.) The material cause is not only the material out of which something is made, but it is also the subject of change: it is the thing that undergoes the change and results in the new form, like the statue’s new shape in the case of the bronze statue. Aristotle reached this induction by noting that in every change, there is something that receives the new form, a something that, until then, has the potency to reach a new actualization. Without the matter, there wouldn’t be anything to change, nothing to be present during the change, and nothing there to be the result of the change. Due to this, he viewed the material of a thing to be a true sort of “cause.”

The formal cause, “that into which,” is the shape of a statue, the cohesion, organization and function of a living thing, the “statement of the essence, and its genera,” and “the parts in the definition.” (The formal cause of a living thing is its cohesion and organization, and what makes it fundamentally different from a corpse is the latter’s lack of cohesion; a corpse is, essentially, a collection of substances, a heart, stomach, arms, etc. but without any integration or function, as it cannot do the kinds of things that living things regularly do.) As the matter is what has the potential for change, the form is the actual change, and combines with the matter in the final result of the change. The form is the arrangement of parts in a substance that make it essentially the kind of thing it is, whether it is something static, like a house, or active, like a tree or an animal. The blueprint of a house, the soul of an animal, a wise general’s plan for the victory of his side in a war, the arrangement of letters in a syllable, the placement and meaning of premises in an argument, these are all formal causes.

These two, the material and the formal, are the causes of the components of substances, their form and matter, during any change (as well as before and after). But Aristotle realized that the process of change itself has sources and causes, and it is this kind of observation, coupled with his study of the history of philosophy, that allowed him to induce the two causes operative in any process of changing or movement: the efficient and the final causes.

Walking in relation to being healthy and to the bowels being evacuated; the father in relation to the child; the adviser in relation to the person who acts on the advice; the doctor in relation to the healthy patient; and “generally what makes of what is made and what causes change of what is changed,” are all efficient causes, “that by which.” The efficient cause is the means or activity or instrument by which a process of change or rest occurs. The doctor is the efficient cause of a healthy patient, because he enacts the procedures required to restore the ill patient’s health; the art of bronze-casting is the efficient cause of a statue, because it is the application of that artistic knowledge which enables a person to create a specific kind of statue.

Lastly, there’s the final cause, “that for the sake of which,” the end or goal of a process that the process is directed towards or someone is meaning to bring about. Health is the final cause of walking; a speech is the final cause of an orator. A sculptor creates a statue so that he can earn money, and this payment is the final cause of the production of the statue. The final cause is “what is best and the end of the things that lead up to it.” (Physics, book 2, part 3)

Some Applications of the Theory

Having established his theory of four causes, he applies the theory to all kinds of phenomena, and even spirals back to the individual four causes to further integrate them, thus gaining new insights on all four of them.

• The construction of a house, for instance, can be completely explained by the metals, brick, building instruments (the material cause), the plan or blueprint for the completed house (the formal cause), the construction of the walls and roof, the laying of the bricks by the builders (the efficient cause), and the finished product of the house (the final cause). In this way, Aristotle could now give a systematic presentation of the causes of a given thing, something which his predecessors could not do, as Aristotle himself reminds us.

• He notes that causes can act reciprocally on each other, in that fitness can allow one to carry out hard work, and, vice versa, hard work can cause fitness. He further points out that this reciprocal causation doesn’t imply that the causal factors are always the same kind of cause: in one case, fitness is the efficient cause of hard work, which is the end result or final cause, but in the other case, hard work is the efficient cause of the end or final cause, which is fitness.

• He observes that the final causes in nature are internal to the things undergoing change. Fruit in a tree, for instance, doesn’t grow to be consumed by humans and other animals (which would be external to the fruit), but to generate another tree (through its seed). Connected with this point, Aristotle remarks that the final and formal cause often coincide, e.g. the principle responsible for the generation of a man is a fully developed member of the same kind or species, i.e. a man who has the same form (formal cause) as the end of the generation (final cause): another man.

• Another insight he has is that the same thing can be the efficient cause of contrary results. A thing which, by its presence, brings about one kind of result is blamed for the contrary result occurring by its absence. Food can be the efficient cause of an animal’s ability to survive, and the efficient cause of an animal’s death when it is absent, which is commonly called “death by starvation.” Aristotle himself presents a clear example of this point: “Thus we ascribe the wreck of a ship to the absence of the pilot whose presence was the [efficient] cause of its safety.” (ibid., words in brackets are mine.)

• A very important implication of his view of causes is that there is, in every case of change, a primary cause that takes priority over the other causes, and often this primary cause is the final/formal cause. In his Parts of Animals, book 1, part 1, he points out that in the case of natural generation (the creation of a new plant or animal), the final cause has explanatory priority over the efficient cause because it is the reason why the plant or animal is what it is. He draws on an analogy with the human arts: you can’t understand the reason for the house-building practices (the efficient cause) without knowing about the intended final result—the complete house (the final cause). In a similar way, the best way to explain how a living thing is generated, or why its parts are formed the way they are, is to refer to the end result of the generation: a certain substance of a certain type.

Dr. Andrea Falcon, a philosopher at Concordia University, wrote an excellent summary of one of the ways that Aristotle handled his predecessor’s opposing view on the priority of the final/formal cause:
From Aristotle we learn that Empedocles [a Pre-Socratic] explained the articulation of the human spine into vertebrae as the result of the twisting and turning that takes place when the fetus is in the womb of the mother. Aristotle finds this explanation unacceptable ([Parts of Animals] 640 a 19–26). To begin with, the fetus must have the power [the very capacity] to twist and turn in the way it does, and Empedocles does not have an explanation for this fact. Secondly, and more importantly, Empedocles overlooks the fact that it takes a man to generate a man. That is to say, the originating principle of the generation is a fully developed man which is formally the same as the final outcome of the process of generation. It is only by looking at the fully developed man that we can understand why our spine is articulated into vertebrae and why the vertebrae are arranged in the particular way they are. This amounts to finding the role that the spine has in the life of a fully developed man. Moreover, it is only by looking at the fully developed man that we can explain why the formation of the vertebrae takes place in the particular way it does.
(Falcon, Andrea, "Aristotle on Causality", The Stanford Encyclopedia of Philosophy (Spring 2011 Edition), Edward N. Zalta (ed.), URL = . )
• One final point about his theory of four causes is that not every process of change has all four of the causes as explanations for it (this despite the mistaken belief of some of Aristotle’s readers). An example Aristotle gives is the eclipse of the moon (Metaphysics, book 8, part 4), an event that he says has no final cause or material cause; rather, he explains it through its efficient cause: the blocking of light by the interposition of the earth between the light source, the sun, and the moon. In this case, the efficient cause has the explanatory priority, and becomes nearly synonymous with the formal cause, the “definitory formula” of an eclipse, as he calls it. (For the formal cause, Aristotle says that it is the “deprivation of light,” but that is too obscure in this case, e.g. a wall would deprive a room of light, but that isn’t the same thing as the eclipse of the moon. As for the material cause, he says that the eclipse has no material cause because it is the moon that is eclipsed: the eclipse itself has no material properties. See ibid.)

Two Objections to the Theory of Four Causes

1. Final Causes are Superfluous

Consider an objection that the Pre-Socratics would have probably leveled against Aristotle regarding his view of final causes: “why should not nature work, not for the sake of something, nor because it is better so, but just as the sky rains, not in order to make the corn grow, but of necessity?” (Physics, book 2, part 8) Why can’t nature operate through strict necessity, and the results that we think happen due to “purpose” are merely coincidences, e.g., the rain that falls from the previously cooled air in the sky coincidentally nourishes a farmer’s crops? In other words, why can’t nature work through only material and efficient causes? Whence is the importance of final causes?

Aristotle responds to this with the example of teeth: “the front teeth sharp, fitted for tearing, the molars broad and useful for grinding down the food.” (ibid.) When an animal grows with this arrangement of teeth, it lives, but when it does not grow this way, it dies. The objector would hold that the relation between the dental arrangement of the animal, and its living or dying, are merely coincidental.

Aristotle, however, notes the causal connection between the formation of the teeth and the needs of the animal: this kind of occurrence happens regularly, and requires an explanation by the objector. He gives more examples of regularly occurring events: frequent rain in winter, and heat in the “dog-days” (i.e. summer). These things don’t happen coincidentally or by chance, and he argues that his opponents must agree with him on this point: we call it chance or coincidence when there’s frequent rain in the summer, or heat in the winter. “For teeth and all other natural things either invariably or normally [i.e. “for the most part”] come about in a given way; but [no instances of spontaneous or chance events are invariable or occur ‘for the most part’],” so coincidences cannot be used to explain events that happen naturally and regularly. (See “Aristotle on Causality.” Words in brackets are mine.) Rather than coincidences, Aristotle concludes this part of his reply by saying that if things occur either coincidentally or for an end, and if regularly occurring natural events are not coincidental, then they must consequently be for an end, an end that is set naturally.

The second part of his reply relates intelligent action to natural events: if houses could be made by nature, then they would be made in the same way as they are now in art (a product of intelligent action), just as if something made by nature were also made by art, that thing would be the same by art as it is in nature. (A recent modern example is animal cloning, which is the artificial recreation of something that is regularly formed through natural processes.) Both intelligent action and nature operate in such a way that one step in a series is done for the sake of the next, and when a series is completed, all the preceding steps are for the sake of the end. Aristotle shows that this insight applies to beings who can’t deliberate (carry out intelligent action), to animals and even plants: birds develop wings for the sake of flight, evading predators, and attacking prey; crustaceans have claws for the sake of grasping objects in place of hands; plants grow leaves for the sake of shading fruit; and plants also grow their roots down (not up) into the ground for nourishment. (Physics, book 2, part 8, and Parts of Animals, book 4, part 8. Some examples are my own.) These things all occur naturally, and for an end, an end set by the nature of the thing acting. Without Aristotle’s account of final causation, all of these connections would be lost, and like Empedocles’ example of the spine, we can easily mislead ourselves about the causes of events if we refrain from looking at the ultimate good or end of natural events.

2. Spontaneity and Chance Vs. Causality

In Physics, book 2, parts 4-6, Aristotle raises and answers a reasonable objection about his account of causality: if his theory accounts for all the types of causes, then how can it deal with spontaneity and chance? Sometimes, spontaneity and chance are thought to be a type of cause, while other people believe that they don’t exist (e.g. “nothing happens by chance,” “there are no accidents”). Indeed, others think that chance is a cause, but one that can’t be penetrated and understood by human intelligence, due to its divine and mysterious nature. So, as Aristotle says, “we must inquire what chance and spontaneity are, whether they are the same or different, and how they fit into our division of causes.”

First, Aristotle holds that we have to distinguish chance events from both (a) invariable events (things that happen “by necessity and always”) and (b) normal events (things that happen “for the most part”). If chance and spontaneity do exist, then they must cover (c) abnormal events, which correspond to what people say when something happens that isn’t invariable or normal: they say that it happens “by chance.”

Secondly, Aristotle connects chance events to his earlier insight that both natural and artificial (things caused by human intelligence) events have final causes—the events occur for the sake of something. Some of these events that are “for the sake of something” happen incidentally, or “by chance,” and so things can be causes “in virtue of themselves” or “incidentally.” The capacity to build a house is, in virtue of itself, the cause of a house, but the person’s other qualities, such as being pale-skinned or musical, would only be an “incidental cause,” i.e., it just so happens that the house-builder is also pale and skilled in music. So chance events are things that happen for the sake of something that also happen incidentally.

Now, we have enough general information about spontaneity and chance to learn more about how they are similar and different.

“Spontaneity” is the wider term, and “chance” is a sub-division of the former: all chance events are spontaneous, but not all spontaneous events are “by chance.”

Spontaneity occurs when something happens (1) for the sake of something, (2) is incidental (in that the final cause is different from what actually results), and (3) has an external cause. Chance occurs when, in addition to these three, the event involves (4) purpose and intention (and thus intelligent reflection/deliberation by a person), and (5) a person capable of moral action. So, if a person wants to raise funds for a feast (the final cause), meets someone else for an unrelated reason, but ends up collecting funds from that person anyway, it is said that the money collection was “by chance.” But if a horse runs to a place and, inadvertently, saves its life from a nearby collapsing building, the running wasn’t done “by chance,” but was “spontaneous,” because the horse isn’t capable of moral action or deliberation. Chance can only happen to people who deliberate and carry out moral actions, but spontaneous events can happen to people capable of moral actions, children (whom are not capable of such actions in Aristotle’s view), lower animals, and even many inanimate objects. If a stone falls and just so happens to strike a man on the way down, but not due to any human intent or action, then it is said to have happened “spontaneously.”

With all of this knowledge, Aristotle can now answer the concerns about chance and spontaneity that he brought up at the beginning. The people who believed that chance and spontaneity were causes were right, because they are both incidental causes, as Aristotle already reasoned. On the other hand, the people who believed that chance and spontaneity aren’t really causes at all are correct in a way, too: both chance and spontaneity are incidental causes, and such causes do not really cause anything in an unqualified way. A flute-player can also be the cause of a house by chance, but only in virtue of the flute-player being a house-builder as well. (Physics, book 2, part 5.) And the mysterious quality surrounding spontaneity and chance can be explained by the fact that the reasons why an incidental event happened can be innumerable; the man who incidentally collected money for his feast could have gone to the place where the incident happened for any number of reasons, such as going to see a friend, a business partner, to escape arrest, or to assist an injured man, etc.

As for where spontaneity and chance fit in with Aristotle’s four causes: they both are efficient causes, “sources of change,” because both can occur for the sake of something (a final cause), but in their cases the events happen for an incidental reason. The horse and its activity of running is the efficient cause of its safety, but it is also the incidental, spontaneous cause, because it did not run in order to be safe. You are the efficient cause of a man being saved from drowning under a bridge, but it’s an incidental cause because you didn’t originally come to the bridge to save anyone.


So ends another monumental set of inductions Aristotle worked on and contributed to philosophy and to the field of science. Here as always, Aristotle uses inductive reasoning as only a master could, connecting the phenomenon of change with philosophical views on causes in a way that solves long-standing problems and helps make the world intelligible. I hope this was helpful for understanding why he even came up with the theory in the first place.


  1. Hello Roderick,

    My apologies; I'm looking for a way to get in contact with you regarding your essay on Objectivism as an open system vs. closed system, and I do not know your email.

    Would you mind writing to me at

    Much obliged,


  2. I'm a sophomore in college studying philosophy and theology. This was very helpful to me for understanding Aristotle's Physics. Thank you so much!

    1. You're very welcome.

      A have a couple of other essays on Aristotle, if you're interested.

      I have an essay on Aristotle's theory of induction, "Aristotle's View of Induction: A Summary."

      And one on how Aristotle discovered logic, "Induction of Objectivity (Aristotle)"

  3. Thank-you so much! My lecturer made me more confused after reading the text. You have clarified a lot of things.

    1. Thanks! I really enjoyed writing it. Definitely appreciated Aristotle a lot more after researching and writing this essay.