Roman copy in marble of a Greek bronze bust of Aristotle by Lysippus, c. 330 BCE.
322 BCE (aged 62)
Era Ancient philosophy
Region Western philosophy
Aristotle (/ˈærɪˌstɒtəl/; Greek: Ἀριστοτέλης [aristotélɛːs], Aristotélēs; 384 – 322 BCE) was a Greek philosopher born in Stagirus, northern Greece, in 384 BCE. His father, Nicomachus, died when Aristotle was a child, whereafter he lived under a guardian's[who?] care. At eighteen, he joined Plato’s Academy in Athens and remained there until the age of thirty-seven (c. 347 BCE). His writings cover many subjects – including physics, biology, zoology, metaphysics, logic, ethics, aesthetics, poetry, theater, music, rhetoric, linguistics, politics and government – and constitute the first comprehensive system of Western philosophy. Shortly after Plato died, Aristotle left Athens and, at the request of Philip of Macedonia, tutored Alexander the Great between 356 and 323 BCE. According to the Encyclopædia Britannica, “Aristotle was the first genuine scientist in history. ... Every scientist is in his debt.”
Teaching Alexander the Great gave Aristotle many opportunities and an abundance of supplies. He established a library in the Lyceum which aided in the production of many of his hundreds of books. The fact that Aristotle was a pupil of Plato contributed to his former views of Platonism, but, following Plato’s death, Aristotle immersed himself in empirical studies and shifted from Platonism to empiricism. He believed all peoples' concepts and all of their knowledge was ultimately based on perception. Aristotle’s views on natural sciences represent the groundwork underlying many of his works.
Aristotle's views on physical science profoundly shaped medieval scholarship. Their influence extended into the Renaissance and were not replaced systematically until the Enlightenment and theories such as classical mechanics. Some of Aristotle's zoological observations were not confirmed or refuted until the 19th century.[examples needed] His works contain the earliest known formal study of logic, which was incorporated in the late 19th century into modern formal logic.
In metaphysics, Aristotelianism profoundly influenced Judeo-Islamic philosophical and theological thought during the Middle Ages and continues to influence Christian theology, especially the scholastic tradition of the Catholic Church. Aristotle was well known among medieval Muslim intellectuals and revered as "The First Teacher" (Arabic: المعلم الأول).
His ethics, though always influential, gained renewed interest with the modern advent of virtue ethics. All aspects of Aristotle's philosophy continue to be the object of active academic study today. Though Aristotle wrote many elegant treatises and dialogues – Cicero described his literary style as "a river of gold" – it is thought that only around a third of his original output has survived.
Aristotle, whose name means "the best purpose", was born in 384 BCE in Stagira, Chalcidice, about 55 km (34 mi) east of modern-day Thessaloniki. His father Nicomachus was the personal physician to King Amyntas of Macedon. Although there is little information on Aristotle's childhood, he probably spent some time within the Macedonian palace, making his first connections with the Macedonian monarchy.
At about the age of eighteen, Aristotle moved to Athens to continue his education at Plato's Academy. He remained there for nearly twenty years before leaving Athens in 348/47 BCE. The traditional story about his departure records that he was disappointed with the Academy's direction after control passed to Plato's nephew Speusippus, although it is possible that he feared anti-Macedonian sentiments and left before Plato had died. Aristotle and Plato's compatibility has been a strongly debated topic. Recently, Harold Cherniss summarized Aristotle's Platonism from the standpoint of classicist Werner Jaeger, stating that: "Jaeger, in whose eyes Plato's philosophy was the "matter" out of which the newer and higher form of Aristotle's thought proceeded by a gradual but steady and undeviating development (Aristotles, p. 11), pronounced the "old controversy", whether or not Aristotle understood Plato, to be "absolut verstandnislos" ["absolutely ?understandable"]. Yet this did not prevent Leisegang[who?] from reasserting that Aristotle's own pattern of thinking was incompatible with a proper understanding of Plato." Contrary to Leisegang's sympathies, Jaeger was sympathetic to a compatible reading of Aristotle and Plato.
Aristotle then accompanied Xenocrates to the court of his friend Hermias of Atarneus in Asia Minor. There, he traveled with Theophrastus to the island of Lesbos, where together they researched the botany and zoology of the island. Aristotle married Pythias, either Hermias's adoptive daughter or niece. She bore him a daughter, whom they also named Pythias. Soon after Hermias' death, Aristotle was invited by Philip II of Macedon to become the tutor to his son Alexander in 343 BCE.
An early Islamic portrayal of Aristotle (right) and Alexander the Great.
Aristotle was appointed as the head of the royal academy of Macedon. During that time he gave lessons not only to Alexander, but also to two other future kings: Ptolemy and Cassander. Aristotle encouraged Alexander toward eastern conquest and his attitude towards Persia was unabashedly ethnocentric. In one famous example, he counsels Alexander to be "a leader to the Greeks and a despot to the barbarians, to look after the former as after friends and relatives, and to deal with the latter as with beasts or plants".
By 335 BCE, Artistotle had returned to Athens, establishing his own school there known as the Lyceum. Aristotle conducted courses at the school for the next twelve years. While in Athens, his wife Pythias died and Aristotle became involved with Herpyllis of Stagira, who bore him a son whom he named after his father, Nicomachus. According to the Suda, he also had an eromenos, Palaephatus of Abydus.
This period in Athens, between 335 and 323 BCE, is when Aristotle is believed to have composed many of his works. He wrote many dialogues of which only fragments have survived. Those works that have survived are in treatise form and were not, for the most part, intended for widespread publication; they are generally thought to be lecture aids for his students. His most important treatises include Physics, Metaphysics, Nicomachean Ethics, Politics, De Anima (On the Soul) and Poetics.
Aristotle not only studied almost every subject possible at the time, but made significant contributions to most of them. In physical science, Aristotle studied anatomy, astronomy, embryology, geography, geology, meteorology, physics and zoology. In philosophy, he wrote on aesthetics, ethics, government, metaphysics, politics, economics, psychology, rhetoric and theology. He also studied education, foreign customs, literature and poetry. His combined works constitute a virtual encyclopedia of Greek knowledge.
Near the end of his life, Alexander became paranoid and wrote threatening letters to Aristotle. Aristotle had made no secret of his contempt for Alexander's pretense of divinity and the king had executed Aristotle's grandnephew Callisthenes as a traitor. A widespread tradition in antiquity suspected Aristotle of playing a role in Alexander's death, but there is little evidence.
Following Alexander's death, anti-Macedonian sentiment in Athens was rekindled. In 322 BCE, Eurymedon the Hierophant denounced Aristotle for not holding the gods in honor, prompting him to flee to his mother's family estate in Chalcis, explaining: "I will not allow the Athenians to sin twice against philosophy" – a reference to Athens's prior trial and execution of Socrates. He died in Euboea of natural causes later that same year, having named his student Antipater as his chief executor and leaving a will in which he asked to be buried next to his wife.
In general, the details of the life of Aristotle are not well-established. The biographies of Aristotle written in ancient times are often speculative and historians only agree on a few salient points.
According to Aristotle, memory is the ability to hold a perceived experience in your mind and to have the ability to distinguish between the internal “appearance” and an occurrence in the past. In other words, a memory is a mental picture (phantasm) in which Aristotle defines in De Anima, as an appearance which is imprinted on the part of the body that forms a memory. Aristotle believed an “imprint” becomes impressed on a semi-fluid bodily organ that undergoes several changes in order to make a memory. A memory occurs when a stimuli is too complex that the nervous system (semi-fluid bodily organ) cannot receive all the impressions at once. These changes are the same as those involved in the operations of sensation, common sense, and thinking . The mental picture imprinted on the bodily organ is the final product of the entire process of sense perception. It does not matter if the experience was seen or heard, every experience ends up as a mental image in memory 
Aristotle uses the word “memory” for two basic abilities. First, the actual retaining of the experience in the mnemonic “imprint” that can develop from sensation. Second, the intellectual anxiety that comes with the “imprint” due to being impressed at a particular time and processing specific contents. These abilities can be explained as memory is neither sensation nor thinking because is arises only after a lapse of time. Therefore, memory is of the past,  prediction is of the future, and sensation is of the present. The retrieval of our “imprints” cannot be performed suddenly. A transitional channel is needed and located in our past experiences, both for our previous experience and present experience.
Aristotle proposed that slow-witted people have good memory because the fluids in their brain do not wash away their memory organ used to imprint experiences and so the “imprint” can easily continue. However, they cannot be too slow or the hardened surface of the organ will not receive new “imprints”. He believed the young and the old do not properly develop an “imprint”. Young people undergo rapid changes as they develop, while the elderly’s organs are beginning to decay, thus stunting new “imprints”. Likewise, people who are too quick-witted are similar to the young and the image cannot be fixed because of the rapid changes of their organ. Since intellectual functions are not involved in memory, memories belong to some animals too, but only those in which have perception of time.
Since Aristotle believes people receive all kinds of sense perceptions and people perceive them as images or “imprints”, people are continually weaving together new “imprints” of things they experience. In order to search for these “imprints”, people search the memory itself. Within the memory, if one experience is offered instead of a specific memory, that person will reject this experience until they find what they are looking for. Recollection occurs when one experience naturally follows another. If the chain of "images" is needed, one memory will stimulate the other. If the chain of "images" is not needed, but expected, then it will only stimulate the other memory in most instances. When people recall experiences, they stimulate certain previous experiences until they have stimulated the one that was needed .
Recollection is the self-directed activity of retrieving the information stored in a memory "imprint" after some time has passed. Retrieval of stored information is dependent on the scope of mnemonic capabilities of a being (human or animal) and the abilities the human or animal possesses . Only humans will remember "imprints" of intellectual activity, such as numbers and words. Animals that have perception of time will be able to retrieve memories of their past observations. Remembering involves only perception of the things remembered and of the time passed. Recollection of an "imprint" is when the present experiences a person remembers are similar with elements corresponding in character and arrangement of past sensory experiences. When an "imprint" is recalled, it may bring forth a large group of related "imprints" .
Aristotle believed the chain of thought, which ends in recollection of certain “imprints”, was connected systematically in three sorts of relationships: similarity, contrast, and contiguity. These three laws make up his Laws of Association. Aristotle believed that past experiences are hidden within our mind. A force operates to awaken the hidden material to bring up the actual experience. According to Aristotle, association is the power innate in a mental state, which operates upon the unexpressed remains of former experiences, allowing them to rise and be recalled .
Aristotle portrayed in the 1493 Nuremberg Chronicle as a scholar of the 15th century AD.
Main article: Term logic
For more details on this topic, see Non-Aristotelian logic.
With the Prior Analytics, Aristotle is credited with the earliest study of formal logic, and his conception of it was the dominant form of Western logic until 19th century advances in mathematical logic. Kant stated in the Critique of Pure Reason that Aristotle's theory of logic completely accounted for the core of deductive inference.
Aristotle "says that 'on the subject of reasoning' he 'had nothing else on an earlier date to speak of'". However, Plato reports that syntax was devised before him, by Prodicus of Ceos, who was concerned by the correct use of words. Logic seems to have emerged from dialectics; the earlier philosophers made frequent use of concepts like reductio ad absurdum in their discussions, but never truly understood the logical implications. Even Plato had difficulties with logic; although he had a reasonable conception of a deductive system, he could never actually construct one, thus he relied instead on his dialectic.
Plato believed that deduction would simply follow from premises, hence he focused on maintaining solid premises so that the conclusion would logically follow. Consequently, Plato realized that a method for obtaining conclusions would be most beneficial. He never succeeded in devising such a method, but his best attempt was published in his book Sophist, where he introduced his division method.
Analytics and the Organon
Main article: Organon
What we today call Aristotelian logic, Aristotle himself would have labeled "analytics". The term "logic" he reserved to mean dialectics. Most of Aristotle's work is probably not in its original form, since it was most likely edited by students and later lecturers. The logical works of Aristotle were compiled into six books in about the early 1st century AD:
On Sophistical Refutations
The order of the books (or the teachings from which they are composed) is not certain, but this list was derived from analysis of Aristotle's writings. It goes from the basics, the analysis of simple terms in the Categories, the analysis of propositions and their elementary relations in On Interpretation, to the study of more complex forms, namely, syllogisms (in the Analytics) and dialectics (in the Topics and Sophistical Refutations). The first three treatises form the core of the logical theory stricto sensu: the grammar of the language of logic and the correct rules of reasoning. There is one volume of Aristotle's concerning logic not found in the Organon, namely the fourth book of Metaphysics.
Plato (left) and Aristotle (right), a detail of The School of Athens, a fresco by Raphael. Aristotle gestures to the earth, representing his belief in knowledge through empirical observation and experience, while holding a copy of his Nicomachean Ethics in his hand, whilst Plato gestures to the heavens, representing his belief in The Forms.
For more details on this topic, see Aristotle's theory of universals.
"Aristotle" by Francesco Hayez (1791–1882)
Like his teacher Plato, Aristotle's philosophy aims at the universal. Aristotle's ontology, however, finds the universal in particular things, which he calls the essence of things, while in Plato's ontology, the universal exists apart from particular things, and is related to them as their prototype or exemplar. For Aristotle, therefore, epistemology is based on the study of particular phenomena and rises to the knowledge of essences, while for Plato epistemology begins with knowledge of universal Forms (or ideas) and descends to knowledge of particular imitations of these. For Aristotle, "form" still refers to the unconditional basis of phenomena but is "instantiated" in a particular substance (see Universals and particulars, below). In a certain sense, Aristotle's method is both inductive and deductive, while Plato's is essentially deductive from a priori principles.
In Aristotle's terminology, "natural philosophy" is a branch of philosophy examining the phenomena of the natural world, and includes fields that would be regarded today as physics, biology and other natural sciences. In modern times, the scope of philosophy has become limited to more generic or abstract inquiries, such as ethics and metaphysics, in which logic plays a major role. Today's philosophy tends to exclude empirical study of the natural world by means of the scientific method. In contrast, Aristotle's philosophical endeavors encompassed virtually all facets of intellectual inquiry.
In the larger sense of the word, Aristotle makes philosophy coextensive with reasoning, which he also would describe as "science". Note, however, that his use of the term science carries a different meaning than that covered by the term "scientific method". For Aristotle, "all science (dianoia) is either practical, poetical or theoretical" (Metaphysics 1025b25). By practical science, he means ethics and politics; by poetical science, he means the study of poetry and the other fine arts; by theoretical science, he means physics, mathematics and metaphysics.
If logic (or "analytics") is regarded as a study preliminary to philosophy, the divisions of Aristotelian philosophy would consist of: (1) Logic; (2) Theoretical Philosophy, including Metaphysics, Physics and Mathematics; (3) Practical Philosophy and (4) Poetical Philosophy.
In the period between his two stays in Athens, between his times at the Academy and the Lyceum, Aristotle conducted most of the scientific thinking and research for which he is renowned today. In fact, most of Aristotle's life was devoted to the study of the objects of natural science. Aristotle's metaphysics contains observations on the nature of numbers but he made no original contributions to mathematics. He did, however, perform original research in the natural sciences, e.g., botany, zoology, physics, astronomy, chemistry, meteorology, and several other sciences.
Aristotle's writings on science are largely qualitative, as opposed to quantitative. Beginning in the 16th century, scientists began applying mathematics to the physical sciences, and Aristotle's work in this area was deemed hopelessly inadequate. His failings were largely due to the absence of concepts like mass, velocity, force and temperature. He had a conception of speed and temperature, but no quantitative understanding of them, which was partly due to the absence of basic experimental devices, like clocks and thermometers.
His writings provide an account of many scientific observations, a mixture of precocious accuracy and curious errors. For example, in his History of Animals he claimed that human males have more teeth than females. In a similar vein, John Philoponus, and later Galileo, showed by simple experiments that Aristotle's theory that a heavier object falls faster than a lighter object is incorrect. On the other hand, Aristotle refuted Democritus's claim that the Milky Way was made up of "those stars which are shaded by the earth from the sun's rays," pointing out (correctly, even if such reasoning was bound to be dismissed for a long time) that, given "current astronomical demonstrations" that "the size of the sun is greater than that of the earth and the distance of the stars from the earth many times greater than that of the sun, then ... the sun shines on all the stars and the earth screens none of them."
In places, Aristotle goes too far in deriving 'laws of the universe' from simple observation and over-stretched reason. Today's scientific method assumes that such thinking without sufficient facts is ineffective, and that discerning the validity of one's hypothesis requires far more rigorous experimentation than that which Aristotle used to support his laws.
Aristotle also had some scientific blind spots. He posited a geocentric cosmology that we may discern in selections of the Metaphysics, which was widely accepted up until the 16th century. From the 3rd century to the 16th century, the dominant view held that the Earth was the rotational center of the universe.
Since he was perhaps the philosopher most respected by European thinkers during and after the Renaissance, these thinkers often took Aristotle's erroneous positions as given, which held back science in this epoch. However, Aristotle's scientific shortcomings should not mislead one into forgetting his great advances in the many scientific fields. For instance, he founded logic as a formal science and created foundations to biology that were not superseded for two millennia. Moreover, he introduced the fundamental notion that nature is composed of things that change and that studying such changes can provide useful knowledge of underlying constants.
As quoted from Charles Lyell's Principles of Geology:
He [Aristotle] refers to many examples of changes now constantly going on, and insists emphatically on the great results which they must produce in the lapse of ages. He instances particular cases of lakes that had dried up, and deserts that had at length become watered by rivers and fertilized. He points to the growth of the Nilotic delta since the time of Homer, to the shallowing of the Palus Maeotis within sixty years from his own time ... He alludes ... to the upheaving of one of the Eolian islands, previous to a volcanic eruption. The changes of the earth, he says, are so slow in comparison to the duration of our lives, that they are overlooked; and the migrations of people after great catastrophes, and their removal to other regions, cause the event to be forgotten.
He says [12th chapter of his Meteorics] 'the distribution of land and sea in particular regions does not endure throughout all time, but it becomes sea in those parts where it was land, and again it becomes land where it was sea, and there is reason for thinking that these changes take place according to a certain system, and within a certain period.' The concluding observation is as follows: 'As time never fails, and the universe is eternal, neither the Tanais, nor the Nile, can have flowed for ever. The places where they rise were once dry, and there is a limit to their operations, but there is none to time. So also of all other rivers; they spring up and they perish; and the sea also continually deserts some lands and invades others The same tracts, therefore, of the earth are not some always sea, and others always continents, but every thing changes in the course of tim
Main article: Physics (Aristotle)
Main article: Classical element
Aristotle proposed a fifth element, aether, in addition to the four proposed earlier by Empedocles.
Earth, which is cold and dry; this corresponds to the modern idea of a solid.
Water, which is cold and wet; this corresponds to the modern idea of a liquid.
Air, which is hot and wet; this corresponds to the modern idea of a gas.
Fire, which is hot and dry; this corresponds to the modern ideas of plasma and heat.
Aether, which is the divine substance that makes up the heavenly spheres and heavenly bodies (stars and planets).
Each of the four earthly elements has its natural place. All that is earthly tends toward the center of the universe, i.e., the center of the Earth. Water tends toward a sphere surrounding the center. Air tends toward a sphere surrounding the water sphere. Fire tends toward the lunar sphere (in which the Moon orbits). When elements are moved out of their natural place, they naturally move back towards it. This is "natural motion"—motion requiring no extrinsic cause. So, for example, in water, earthy bodies sink while air bubbles rise up; in air, rain falls and flame rises. Outside all the other spheres, the heavenly, fifth element, manifested in the stars and planets, moves in the perfection of circles.
Main article: potentiality and actuality
Aristotle defined motion as the actuality of a potentiality as such. Aquinas suggested that the passage be understood literally; that motion can indeed be understood as the active fulfillment of a potential, as a transition toward a potentially possible state. Because actuality and potentiality are normally opposites in Aristotle, other commentators either suggest that the wording which has come down to us is erroneous, or that the addition of the "as such" to the definition is critical to understanding it.
Causality, the four causes
Main article: Four causes
Aristotle suggested that the reason for anything coming about can be attributed to four different types of simultaneously active causal factors:
Material cause describes the material out of which something is composed. Thus the material cause of a table is wood, and the material cause of a car is rubber and steel. It is not about action. It does not mean one domino knocks over another domino.
The formal cause is its form, i.e., the arrangement of that matter. It tells us what a thing is, that any thing is determined by the definition, form, pattern, essence, whole, synthesis or archetype. It embraces the account of causes in terms of fundamental principles or general laws, as the whole (i.e., macrostructure) is the cause of its parts, a relationship known as the whole-part causation. Plainly put, the formal cause is the idea existing in the first place as exemplar in the mind of the sculptor, and in the second place as intrinsic, determining cause, embodied in the matter. Formal cause could only refer to the essential quality of causation. A simple example of the formal cause is the mental image or idea that allows an artist, architect, or engineer to create his drawings.
The efficient cause is "the primary source", or that from which the change under consideration proceeds. It identifies 'what makes of what is made and what causes change of what is changed' and so suggests all sorts of agents, nonliving or living, acting as the sources of change or movement or rest. Representing the current understanding of causality as the relation of cause and effect, this covers the modern definitions of "cause" as either the agent or agency or particular events or states of affairs. So, take the two dominoes, this time of equal weighting, the first is knocked over causing the second also to fall over.
The final cause is its purpose, or that for the sake of which a thing exists or is done, including both purposeful and instrumental actions and activities. The final cause or teleos is the purpose or function that something is supposed to serve. This covers modern ideas of motivating causes, such as volition, need, desire, ethics, or spiritual beliefs.
Additionally, things can be causes of one another, causing each other reciprocally, as hard work causes fitness and vice versa, although not in the same way or function, the one is as the beginning of change, the other as the goal. (Thus Aristotle first suggested a reciprocal or circular causality as a relation of mutual dependence or influence of cause upon effect). Moreover, Aristotle indicated that the same thing can be the cause of contrary effects; its presence and absence may result in different outcomes. Simply it is the goal or purpose that brings about an event. Our two dominoes require someone or something to intentionally knock over the first domino, since it cannot fall of its own accord.
Aristotle marked two modes of causation: proper (prior) causation and accidental (chance) causation. All causes, proper and incidental, can be spoken as potential or as actual, particular or generic. The same language refers to the effects of causes, so that generic effects assigned to generic causes, particular effects to particular causes, operating causes to actual effects. Essentially, causality does not suggest a temporal relation between the cause and the effect.
Aristotle held more accurate theories on some optical concepts than other philosophers of his day. The earliest known written evidence of a camera obscura can be found in Aristotle's documentation of such a device in 350 BC in Problemata. Aristotle's apparatus contained a dark chamber that had a single small hole, or aperture, to allow for sunlight to enter. Aristotle used the device to make observations of the sun and noted that no matter what shape the hole was, the sun would still be correctly displayed as a round object. In modern cameras, this is analogous to the diaphragm. Aristotle also made the observation that when the distance between the aperture and the surface with the image increased, the image was magnified.
Chance and spontaneity
According to Aristotle, spontaneity and chance are causes of some things, distinguishable from other types of cause. Chance as an incidental cause lies in the realm of accidental things. It is "from what is spontaneous" (but note that what is spontaneous does not come from chance). For a better understanding of Aristotle's conception of "chance" it might be better to think of "coincidence": Something takes place by chance if a person sets out with the intent of having one thing take place, but with the result of another thing (not intended) taking place.
For example: A person seeks donations. That person may find another person willing to donate a substantial sum. However, if the person seeking the donations met the person donating, not for the purpose of collecting donations, but for some other purpose, Aristotle would call the collecting of the donation by that particular donator a result of chance. It must be unusual that something happens by chance. In other words, if something happens all or most of the time, we cannot say that it is by chance.
There is also more specific kind of chance, which Aristotle names "luck", that can only apply to human beings, since it is in the sphere of moral actions. According to Aristotle, luck must involve choice (and thus deliberation), and only humans are capable of deliberation and choice. "What is not capable of action cannot do anything by chance".
Statue of Aristotle (1915) by Cipri Adolf Bermann at the University of Freiburg im Breisgau
Main article: Metaphysics (Aristotle)
Aristotle defines metaphysics as "the knowledge of immaterial being," or of "being in the highest degree of abstraction." He refers to metaphysics as "first philosophy", as well as "the theologic science."
Substance, potentiality and actuality
See also: Potentiality and actuality (Aristotle)
Aristotle examines the concepts of substance and essence (ousia) in his Metaphysics (Book VII), and he concludes that a particular substance is a combination of both matter and form. In book VIII, he distinguishes the matter of the substance as the substratum, or the stuff of which it is composed. For example, the matter of a house is the bricks, stones, timbers etc., or whatever constitutes the potential house, while the form of the substance is the actual house, namely 'covering for bodies and chattels' or any other differentia (see also predicables) that let us define something as a house. The formula that gives the components is the account of the matter, and the formula that gives the differentia is the account of the form.
With regard to the change (kinesis) and its causes now, as he defines in his Physics and On Generation and Corruption 319b–320a, he distinguishes the coming to be from:
growth and diminution, which is change in quantity;
locomotion, which is change in space; and
alteration, which is change in quality.
The coming to be is a change where nothing persists of which the resultant is a property. In that particular change he introduces the concept of potentiality (dynamis) and actuality (entelecheia) in association with the matter and the form.
Referring to potentiality, this is what a thing is capable of doing, or being acted upon, if the conditions are right and it is not prevented by something else. For example, the seed of a plant in the soil is potentially (dynamei) plant, and if is not prevented by something, it will become a plant. Potentially beings can either 'act' (poiein) or 'be acted upon' (paschein), which can be either innate or learned. For example, the eyes possess the potentiality of sight (innate – being acted upon), while the capability of playing the flute can be possessed by learning (exercise – acting).
Actuality is the fulfillment of the end of the potentiality. Because the end (telos) is the principle of every change, and for the sake of the end exists potentiality, therefore actuality is the end. Referring then to our previous example, we could say that an actuality is when a plant does one of the activities that plants do.
"For that for the sake of which a thing is, is its principle, and the becoming is for the sake of the end; and the actuality is the end, and it is for the sake of this that the potentiality is acquired. For animals do not see in order that they may have sight, but they have sight that they may see."
In summary, the matter used to make a house has potentiality to be a house and both the activity of building and the form of the final house are actualities, which is also a final cause or end. Then Aristotle proceeds and concludes that the actuality is prior to potentiality in formula, in time and in substantiality.
With this definition of the particular substance (i.e., matter and form), Aristotle tries to solve the problem of the unity of the beings, for example, "what is it that makes a man one"? Since, according to Plato there are two Ideas: animal and biped, how then is man a unity? However, according to Aristotle, the potential being (matter) and the actual one (form) are one and the same thing.
Universals and particulars
Main article: Aristotle's theory of universals
Aristotle's predecessor, Plato, argued that all things have a universal form, which could be either a property, or a relation to other things. When we look at an apple, for example, we see an apple, and we can also analyze a form of an apple. In this distinction, there is a particular apple and a universal form of an apple. Moreover, we can place an apple next to a book, so that we can speak of both the book and apple as being next to each other.
Plato argued that there are some universal forms that are not a part of particular things. For example, it is possible that there is no particular good in existence, but "good" is still a proper universal form. Bertrand Russell is a 20th-century philosopher who agreed with Plato on the existence of "uninstantiated universals".
Aristotle disagreed with Plato on this point, arguing that all universals are instantiated. Aristotle argued that there are no universals that are unattached to existing things. According to Aristotle, if a universal exists, either as a particular or a relation, then there must have been, must be currently, or must be in the future, something on which the universal can be predicated. Consequently, according to Aristotle, if it is not the case that some universal can be predicated to an object that exists at some period of time, then it does not exist.
In addition, Aristotle disagreed with Plato about the location of universals. As Plato spoke of the world of the forms, a location where all universal forms subsist, Aristotle maintained that universals exist within each thing on which each universal is predicated. So, according to Aristotle, the form of apple exists within each apple, rather than in the world of the forms.
Biology and medicine
In Aristotelian science, especially in biology, things he saw himself have stood the test of time better than his retelling of the reports of others, which contain error and superstition. He dissected animals but not humans; his ideas on how the human body works have been almost entirely superseded.
Empirical research program
Aristotle is the earliest natural historian whose work has survived in some detail. Aristotle certainly did research on the natural history of Lesbos, and the surrounding seas and neighbouring areas. The works that reflect this research, such as History of Animals, Generation of Animals, and Parts of Animals, contain some observations and interpretations, along with sundry myths and mistakes. The most striking passages are about the sea-life visible from observation on Lesbos and available from the catches of fishermen. His observations on catfish, electric fish (Torpedo) and angler-fish are detailed, as is his writing on cephalopods, namely, Octopus, Sepia (cuttlefish) and the paper nautilus (Argonauta argo). His description of the hectocotyl arm, used in sexual reproduction, was widely disbelieved until its rediscovery in the 19th century. He separated the aquatic mammals from fish, and knew that sharks and rays were part of the group he called Selachē (selachians).
Another good example of his methods comes from the Generation of Animals in which Aristotle describes breaking open fertilized chicken eggs at intervals to observe when visible organs were generated.
He gave accurate descriptions of ruminants' four-chambered fore-stomachs, and of the ovoviviparous embryological development of the hound shark Mustelus mustelus.
Classification of living things
Aristotle's classification of living things contains some elements which still existed in the 19th century. What the modern zoologist would call vertebrates and invertebrates, Aristotle called 'animals with blood' and 'animals without blood' (he did not know that complex invertebrates do make use of hemoglobin, but of a different kind from vertebrates). Animals with blood were divided into live-bearing (humans and mammals), and egg-bearing (birds and fish). Invertebrates ('animals without blood') are insects, crustacea (divided into non-shelled – cephalopods – and shelled) and testacea (molluscs). In some respects, this incomplete classification is better than that of Linnaeus, who crowded the invertebrata together into two groups, Insecta and Vermes (worms).
For Charles Singer, "Nothing is more remarkable than [Aristotle's] efforts to [exhibit] the relationships of living things as a scala naturae" Aristotle's History of Animals classified organisms in relation to a hierarchical "Ladder of Life" (scala naturae or Great Chain of Being), placing them according to complexity of structure and function so that higher organisms showed greater vitality and ability to move.
Aristotle believed that intellectual purposes, i.e., final causes, guided all natural processes. Such a teleological view gave Aristotle cause to justify his observed data as an expression of formal design. Noting that "no animal has, at the same time, both tusks and horns," and "a single-hooved animal with two horns I have never seen," Aristotle suggested that Nature, giving no animal both horns and tusks, was staving off vanity, and giving creatures faculties only to such a degree as they are necessary. Noting that ruminants had multiple stomachs and weak teeth, he supposed the first was to compensate for the latter, with Nature trying to preserve a type of balance.
In a similar fashion, Aristotle believed that creatures were arranged in a graded scale of perfection rising from plants on up to man, the scala naturae. His system had eleven grades, arranged according "to the degree to which they are infected with potentiality", expressed in their form at birth. The highest animals laid warm and wet creatures alive, the lowest bore theirs cold, dry, and in thick eggs.
Aristotle also held that the level of a creature's perfection was reflected in its form, but not preordained by that form. Ideas like this, and his ideas about souls, are not regarded as science at all in modern times.
He placed emphasis on the type(s) of soul an organism possessed, asserting that plants possess a vegetative soul, responsible for reproduction and growth, animals a vegetative and a sensitive soul, responsible for mobility and sensation, and humans a vegetative, a sensitive, and a rational soul, capable of thought and reflection.
Aristotle, in contrast to earlier philosophers, but in accordance with the Egyptians, placed the rational soul in the heart, rather than the brain. Notable is Aristotle's division of sensation and thought, which generally went against previous philosophers, with the exception of Alcmaeon.
The frontispiece to a 1644 version of the expanded and illustrated edition of Historia Plantarum (ca. 1200), which was originally written around 200 BC.
Main articles: Theophrastus and Historia Plantarum
Aristotle's successor at the Lyceum, Theophrastus, wrote a series of books on botany—the History of Plants—which survived as the most important contribution of antiquity to botany, even into the Middle Ages. Many of Theophrastus' names survive into modern times, such as carpos for fruit, and pericarpion for seed vessel.
Rather than focus on formal causes, as Aristotle did, Theophrastus suggested a mechanistic scheme, drawing analogies between natural and artificial processes, and relying on Aristotle's concept of the efficient cause. Theophrastus also recognized the role of sex in the reproduction of some higher plants, though this last discovery was lost in later ages.
Influence on Hellenistic medicine
For more details on this topic, see Medicine in ancient Greece.
After Theophrastus, the Lyceum failed to produce any original work. Though interest in Aristotle's ideas survived, they were generally taken unquestioningly. It is not until the age of Alexandria under the Ptolemies that advances in biology can be again found.
The first medical teacher at Alexandria, Herophilus of Chalcedon, corrected Aristotle, placing intelligence in the brain, and connected the nervous system to motion and sensation. Herophilus also distinguished between veins and arteries, noting that the latter pulse while the former do not. Though a few ancient atomists such as Lucretius challenged the teleological viewpoint of Aristotelian ideas about life, teleology (and after the rise of Christianity, natural theology) would remain central to biological thought essentially until the 18th and 19th centuries. Ernst Mayr claimed that there was "nothing of any real consequence in biology after Lucretius and Galen until the Renaissance." Aristotle's ideas of natural history and medicine survived, but they were generally taken unquestioningly.
Aristotle's psychology, given in his treatise On the Soul (peri psyche, often known by its Latin title De Anima), posits three kinds of soul ("psyches"): the vegetative soul, the sensitive soul, and the rational soul. Humans have a rational soul. This kind of soul is capable of the same powers as the other kinds: Like the vegetative soul it can grow and nourish itself; like the sensitive soul it can experience sensations and move locally. The unique part of the human, rational soul is its ability to receive forms of other things and compare them.
For Aristotle, the soul (psyche) was a simpler concept than it is for us today. By soul he simply meant the form of a living being. Since all beings are composites of form and matter, the form of living beings is that which endows them with what is specific to living beings, e.g. the ability to initiate movement (or in the case of plants, growth and chemical transformations, which Aristotle considers types of movement).
Main article: Aristotelian ethics
Aristotle considered ethics to be a practical rather than theoretical study, i.e., one aimed at becoming good and doing good rather than knowing for its own sake. He wrote several treatises on ethics, including most notably, the Nicomachean Ethics.
Aristotle taught that virtue has to do with the proper function (ergon) of a thing. An eye is only a good eye in so much as it can see, because the proper function of an eye is sight. Aristotle reasoned that humans must have a function specific to humans, and that this function must be an activity of the psuchē (normally translated as soul) in accordance with reason (logos). Aristotle identified such an optimum activity of the soul as the aim of all human deliberate action, eudaimonia, generally translated as "happiness" or sometimes "well being". To have the potential of ever being happy in this way necessarily requires a good character (ēthikē aretē), often translated as moral (or ethical) virtue (or excellence).
Aristotle taught that to achieve a virtuous and potentially happy character requires a first stage of having the fortune to be habituated not deliberately, but by teachers, and experience, leading to a later stage in which one consciously chooses to do the best things. When the best people come to live life this way their practical wisdom (phronesis) and their intellect (nous) can develop with each other towards the highest possible human virtue, the wisdom of an accomplished theoretical or speculative thinker, or in other words, a philosopher.
Main article: Politics (Aristotle)
Like Aristotle, conservatives generally accept the world as it is; they distrust the politics of abstract reason – that is, reason divorced from experience.
— Benjamin Wiker
In addition to his works on ethics, which address the individual, Aristotle addressed the city in his work titled Politics. Aristotle considered the city to be a natural community. Moreover, he considered the city to be prior in importance to the family which in turn is prior to the individual, "for the whole must of necessity be prior to the part". He also famously stated that "man is by nature a political animal". Aristotle conceived of politics as being like an organism rather than like a machine, and as a collection of parts none of which can exist without the others. Aristotle's conception of the city is organic, and he is considered one of the first to conceive of the city in this manner.
The common modern understanding of a political community as a modern state is quite different from Aristotle's understanding. Although he was aware of the existence and potential of larger empires, the natural community according to Aristotle was the city (polis) which functions as a political "community" or "partnership" (koinōnia). The aim of the city is not just to avoid injustice or for economic stability, but rather to allow at least some citizens the possibility to live a good life, and to perform beautiful acts: "The political partnership must be regarded, therefore, as being for the sake of noble actions, not for the sake of living together." This is distinguished from modern approaches, beginning with social contract theory, according to which individuals leave the state of nature because of "fear of violent death" or its "inconveniences."
Rhetoric and poetics
Main articles: Rhetoric (Aristotle) and Poetics (Aristotle)
Aristotle considered epic poetry, tragedy, comedy, dithyrambic poetry and music to be imitative, each varying in imitation by medium, object, and manner. For example, music imitates with the media of rhythm and harmony, whereas dance imitates with rhythm alone, and poetry with language. The forms also differ in their object of imitation. Comedy, for instance, is a dramatic imitation of men worse than average; whereas tragedy imitates men slightly better than average. Lastly, the forms differ in their manner of imitation – through narrative or character, through change or no change, and through drama or no drama. Aristotle believed that imitation is natural to mankind and constitutes one of mankind's advantages over animals.
While it is believed that Aristotle's Poetics comprised two books – one on comedy and one on tragedy – only the portion that focuses on tragedy has survived. Aristotle taught that tragedy is composed of six elements: plot-structure, character, style, thought, spectacle, and lyric poetry. The characters in a tragedy are merely a means of driving the story; and the plot, not the characters, is the chief focus of tragedy. Tragedy is the imitation of action arousing pity and fear, and is meant to effect the catharsis of those same emotions. Aristotle concludes Poetics with a discussion on which, if either, is superior: epic or tragic mimesis. He suggests that because tragedy possesses all the attributes of an epic, possibly possesses additional attributes such as spectacle and music, is more unified, and achieves the aim of its mimesis in shorter scope, it can be considered superior to epic.
Aristotle was a keen systematic collector of riddles, folklore, and proverbs; he and his school had a special interest in the riddles of the Delphic Oracle and studied the fables of Aesop.
Views on women
Main article: Aristotle's views on women
Aristotle's analysis of procreation describes an active, ensouling masculine element bringing life to an inert, passive female element. On this ground, feminists have accused Aristotle of misogyny and sexism. However, Aristotle gave equal weight to women's happiness as he did to men's, and commented in his Rhetoric that a society cannot be happy unless women are happy too.
Loss and preservation of his works
See also: Corpus Aristotelicum
Modern scholarship reveals that Aristotle's "lost" works stray considerably in characterization from the surviving Aristotelian corpus. Whereas the lost works appear to have been originally written with an intent for subsequent publication, the surviving works do not appear to have been so. Rather the surviving works mostly resemble lecture notes unintended for publication. The authenticity of a portion of the surviving works as originally Aristotelian is also today held suspect, with some books duplicating or summarizing each other, the authorship of one book questioned and another book considered to be unlikely Aristotle's at all.
Some of the individual works within the corpus, including the Constitution of Athens, are regarded by most scholars as products of Aristotle's "school," perhaps compiled under his direction or supervision. Others, such as On Colors, may have been produced by Aristotle's successors at the Lyceum, e.g., Theophrastus and Straton. Still others acquired Aristotle's name through similarities in doctrine or content, such as the De Plantis, possibly by Nicolaus of Damascus. Other works in the corpus include medieval palmistries and astrological and magical texts whose connections to Aristotle are purely fanciful and self-promotional.
According to a distinction that originates with Aristotle himself, his writings are divisible into two groups: the "exoteric" and the "esoteric". Most scholars have understood this as a distinction between works Aristotle intended for the public (exoteric), and the more technical works intended for use within the school (esoteric). Modern scholars commonly assume these latter to be Aristotle's own (unpolished) lecture notes (or in some cases possible notes by his students). However, one classic scholar offers an alternative interpretation. The 5th century neoplatonist Ammonius Hermiae writes that Aristotle's writing style is deliberately obscurantist so that "good people may for that reason stretch their mind even more, whereas empty minds that are lost through carelessness will be put to flight by the obscurity when they encounter sentences like these."