Four causes
The four causes or four explanations are, in Aristotelian thought, categories of questions that explain "the why's" of something that exists or changes in nature. The four causes are the: material cause, the formal cause, the efficient cause, and the final cause. Aristotle wrote that "we do not have knowledge of a thing until we have grasped its why, that is to say, its cause." While there are cases in which classifying a "cause" is difficult, or in which "causes" might merge, Aristotle held that his four "causes" provided an analytical scheme of general applicability.
Aristotle's word aitia has, in philosophical scholarly tradition, been translated as 'cause'. This peculiar, specialized, technical, usage of the word 'cause' is not that of everyday English language. Rather, the translation of Aristotle's αἰτία that is nearest to current ordinary language is "explanation."
In Physics II.3, I.7-9 and Metaphysics V.2, Aristotle holds that there are four kinds of answers to "why" questions:
;Matter: The material cause of a change or movement. Aristotle defines matter as, "...the primary substratum of each thing, from which it comes to be per se, , and that persists in the result." - Physics I.9. Matter is what allows a thing to change, either accidentally, such as a change in shape, or substantially, such as the death of a living thing, or a compound returning to its elemental parts. Aristotle gives the examples of a table's matter being wood, or a statue's matter being bronze or marble.
;Form: The formal cause of a change or movement. Aristotle defines form as, "...the terminus of the process of ." - Metaphysics V.4. It is what something changes into, i.e. what makes a thing what it is. Form is often confused with the whole substance, whereas it is a thing's essential difference, for example, man is a rational animal, what makes man a man, is his rationality, i.e. what makes him different from other animals.
;Efficient, or Agent: The efficient or moving cause of a change or movement. This consists of things apart from the thing being changed or moved, which interact so as to be an agency of the change or movement. For example, the efficient cause of a table is a carpenter, or a person working as one, and according to Aristotle the efficient cause of a child is a parent.
;Final Cause, or End: The final cause of a change or movement. This is a change or movement for the sake of a thing to be what it is. For a seed, it might be an adult plant; for a sailboat, it might be sailing; for a ball at the top of a ramp, it might be coming to rest at the bottom. Often the final cause is confused with a purpose, or intention, but this is not the case, since a purpose is the effect wanted for a thing by a person, whereas Aristotle thought of ends as always present, ungiven, and always good.
The four "causes" are not mutually exclusive. For Aristotle, several, preferably four, answers to the question "why" have to be given to explain a phenomenon and especially the actual configuration of an object. For example, if asking why a table is such and such, an explanation in terms of the four causes would sound like this: This table is solid and brown because it is made of wood ; it does not collapse because it has four legs of equal length ; it is as it is because a carpenter made it, starting from a tree ; it has these dimensions because it is to be used by humans.
Aristotle distinguished between intrinsic and extrinsic causes. Matter and form are intrinsic causes because they deal directly with the object, whereas efficient and finality causes are said to be extrinsic because they are external.
Thomas Aquinas demonstrated that only those four types of causes can exist and no others. He also introduced a priority order according to which "matter is made perfect by the form, form is made perfect by the agent, and agent is made perfect by the finality." Hence, the finality is the cause of causes or, equivalently, the queen of causes.
Definition of "cause"
In his philosophical writings, Aristotle used the Greek word αἴτιον, a neuter singular form of an adjective. The Greek word had meant, perhaps originally in a "legal" context, what or who is "responsible," mostly but not always in a bad sense of "guilt" or "blame." Alternatively, it could mean "to the credit of" someone or something. The appropriation of this word by Aristotle and other philosophers reflects how the Greek experience of legal practice influenced the concern in Greek thought to determine what is responsible. The word developed other meanings, including its use in philosophy in a more abstract sense.Aristotle, in The Metaphysics V.3, defines a cause as, "...that from which, as something intrinsic, a thing comes to be..." Some later scholastics redefined a cause as, "that from which something proceeds."
Aristotle's "four causes"
Aristotle used the four causes to provide different answers to the question, "because of what?" The four answers to this question illuminate different aspects of how a thing comes into being or of how an event takes place.Material
Aristotle considers the material "cause" of an object as equivalent to the nature of the raw material out of which the object is composed.Whereas modern physics looks to simple bodies, Aristotle's physics took a more general viewpoint, and treated living things as exemplary. Nevertheless, he argued that simple natural bodies such as earth, fire, air, and water also showed signs of having their own innate sources of motion, change, and rest. Fire, for example, carries things upwards, unless stopped from doing so. Things formed by human artifice, such as beds and cloaks, have no innate tendency to become beds or cloaks.
In traditional Aristotelian philosophical terminology, material is not the same as substance. Matter has parallels with substance in so far as primary matter serves as the substratum for simple bodies which are not substance: sand and rock, rivers and seas, atmosphere and wind. In this traditional terminology, 'substance' is a term of ontology, referring to really existing things; only individuals are said to be substances in the primary sense. Secondary substance, in a different sense, also applies to man-made artifacts.
Formal
Aristotle considers the formal "cause" as the internal cause by which a thing is what it is. Often, form is confused with what Aristotelians call accidental form, i.e. what makes an inhering part what it is. Some say that form is the arrangement or shape of a thing, but this is not the case, since Aristotle would define these things as accidents,, while he defines form as the principle of a substance. This mistake is made because, with some things, what makes them what they are is their accidents. These things are called accidental beings. For things such as a three-legged stool, what makes it what it is is the number of legs it has, which is a quantity. But for other things, such as a bowl, if defined as a tool which has the ability to hold liquids, what makes it what it is is not its shape, but its ability to hold liquids, since its shape could change, and it could still have its ability.By Aristotle's own account, this is a difficult and controversial concept. It links with theories of forms such as those of Aristotle's teacher, Plato, but in Aristotle's own account, he takes into account many previous writers who had expressed opinions about forms and ideas, but he shows how his own views differ from them.
Efficient
Aristotle defines the agent or efficient "cause" of an object as that which causes change and drives transient motion . In many cases, this is simply the thing that brings something about. For example, in the case of a statue, it is the person chiseling away which transforms a block of marble into a statue. According to Lloyd, of the four causes, only this one is what is meant by the modern English word "cause" in ordinary speech.Final
Aristotle defines the end, purpose, or final "cause" as that for the sake of which a thing is done. Like the form, this is a controversial type of explanation in science; some have argued for its survival in evolutionary biology, while Ernst Mayr denied that it continued to play a role. It is commonly recognized that Aristotle's conception of nature is teleological in the sense that Nature exhibits functionality in a more general sense than is exemplified in the purposes that humans have. Aristotle observed that a telos does not necessarily involve deliberation, intention, consciousness, or intelligence:According to Aristotle, a seed has the eventual adult plant as its end if and only if the seed would become the adult plant under normal circumstances. In Physics II.9, Aristotle hazards a few arguments that a determination of the end of a phenomenon is more important than the others. He argues that the end is that which brings it about, so for example "if one defines the operation of sawing as being a certain kind of dividing, then this cannot come about unless the saw has teeth of a certain kind; and these cannot be unless it is of iron." According to Aristotle, once a final "cause" is in place, the material, efficient and formal "causes" follow by necessity. However, he recommends that the student of nature determine the other "causes" as well, and notes that not all phenomena have an end, e.g., chance events.
Aristotle saw that his biological investigations provided insights into the causes of things, especially into the final cause:
George Holmes Howison highlights "final causation" in presenting his theory of metaphysics, which he terms "personal idealism", and to which he invites not only man, but all life:
However, Edward Feser argues, in line with the Aristotelian and Thomistic tradition, that finality has been greatly misunderstood. Indeed, without finality, efficient causality becomes inexplicable. Finality thus understood is not purpose but that end towards which a thing is ordered.
When a match is rubbed against the side of a matchbox, the effect is not the appearance of an elephant or the sounding of a drum, but fire.
The effect is not arbitrary because the match is ordered towards the end of fire which is realized through efficient causes.
In their biosemiotic study, Stuart Kauffman, Robert K. Logan et al. remark: