Aristotle

Aristotle
Roman copy in marble of a Greek bronze bust of Aristotle by Lysippus, c. 330 BC. The alabaster mantle is modern.
Born	384 BC Stagira, Chalcidice (Chalkidiki), Northern Greece
Died	322 BC (aged 62) Euboea, Greece
Nationality	Greek
Era	Ancient philosophy
Region	Western philosophy
School	Peripatetic school Aristotelianism
Main interests	Biology Zoology Physics Metaphysics Logic Ethics Rhetoric Music Poetry Theatre Politics Government
Notable ideas	Golden mean Aristotelian logic Syllogism Hexis Hylomorphism Theory of the soul
Influences Parmenides Socrates Plato Heraclitus Democritus
Influenced Virtually all subsequent Western philosophy, Christian philosophy and pre-Enlightenment science; also much Islamic and Jewish philosophy (see List of writers influenced by Aristotle)

Aristotelianism
Overview Peripatetic school Physics Ethics Term logic Theology (unmoved mover)
Ideas and interests Correspondence theory of truth Hexis Virtue ethics (golden mean) Four causes Telos Phronesis Eudaimonia Arete Temporal finitism Antiperistasis Philosophy of nature (sublunary sphere) Potentiality and actuality Universals (substantial form) Hylomorphism Mimesis Catharsis Substance (ousia) Essence / Accident Category of being Minima naturalia Magnanimity Sensus communis Rational animal Genus–differentia
Corpus Aristotelicum Physics Organon Nicomachean Ethics Politics Metaphysics On the Soul Rhetoric Poetics
Influences Followers Plato Alexander the Great Theophrastus Avicenna Averroes Maimonides Thomas Aquinas Alasdair MacIntyre Martha Nussbaum
Related topics Platonism Commentaries on Aristotle Scholasticism Conimbricenses Pseudo-Aristotle Views on women
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Aristotle (;^[1] Greek: Ἀριστοτέλης , Aristotélēs; 384 – 322 BC)^[2] was a Greek philosopher and scientist born in the Macedonian city of Stagira, Chalkidice, on the northern periphery of Classical Greece. His father, Nicomachus, died when Aristotle was a child, whereafter Proxenus of Atarneus became his guardian.^[3] At eighteen, he joined Plato's Academy in Athens and remained there until the age of thirty-seven (c. 347 BC). 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 Macedon, tutored Alexander the Great starting from 343 BC.^[4] According to the Encyclopædia Britannica, "Aristotle was the first genuine scientist in history ... [and] every scientist is in his debt."^[5]

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.^[6] 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, such as on the hectocotyl (reproductive) arm of the octopus, were not confirmed or refuted until the 19th century. 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"^[7] – it is thought that only around a third of his original output has survived.^[8]

Life

School of Aristotle in Mieza, Macedonia, Greece

Aristotle, whose name means "the best purpose",^[9] was born in 384 BC in Stagira, Chalcidice, about 55 km (34 miles) east of modern-day Thessaloniki.^[10] 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.^[11]

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 BC. 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 died.^[12]

"Aristotle" by Francesco Hayez (1791–1882)

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 BC.^[4]

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.^[13] 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".^[13]

By 335 BC, 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.^[14]

This period in Athens, between 335 and 323 BC, is when Aristotle is believed to have composed many of his works.^[4] 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 and Aristotle became estranged over Alexander's relationship with Persia and Persians. A widespread tradition in antiquity suspected Aristotle of playing a role in Alexander's death, but there is little evidence.^[15]

Following Alexander's death, anti-Macedonian sentiment in Athens was rekindled. In 322 BC, 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"^[16][17] – 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.^[18]

Charles Walston argues that the tomb of Aristotle is located on the sacred way between Chalcis and Eretria and to have contained two styluses, a pen, a signet-ring and some terra-cottas as well as what is supposed to be the earthly remains of Aristotle in the form of some skull fragments.^[19]

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.^[20]

Thought

Logic

Aristotle portrayed in the 1493 Nuremberg Chronicle as a scholar of the 15th century AD.

With the Prior Analytics, Aristotle is credited with the earliest study of formal logic,^[21] and his conception of it was the dominant form of Western logic until 19th century advances in mathematical logic.^[22] Kant stated in the Critique of Pure Reason that Aristotle's theory of logic completely accounted for the core of deductive inference.

History

Aristotle "says that 'on the subject of reasoning' he 'had nothing else on an earlier date to speak of'".^[23] 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.^[24]

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.^[25]

Analytics and the 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, because 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 CE:

1. Categories
2. On Interpretation
3. Prior Analytics
4. Posterior Analytics
5. Topics
6. 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.^[24]

Aristotle's epistemology

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, while holding a copy of Timaeus

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.^[26]

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.^[27] 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.^[28] 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."^[29]

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.

Because 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.^[30] 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.

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 [31]

Physics

Five elements

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.

Motion

Aristotle defined motion as the actuality of a potentiality as such.^[32] 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.^[33]

Causality, the 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, because 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.

Optics

Aristotle held more accurate theories on some optical concepts than other philosophers of his day. The second oldest written evidence of a camera obscura (after Mozi c. 400 BC) 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.^[34]

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, because 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".^[35]

Metaphysics

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

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.^[36]

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:

1. growth and diminution, which is change in quantity;
2. locomotion, which is change in space; and
3. 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."^[37]

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.^[38]

Universals and particulars

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

Octopus swimming

Torpedo fuscomaculata

Leopard shark

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).^[39]

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.^[40]

Classification of living things

Aristotle distinguished about 500 species of birds, mammals and fishes.^[41][42] His 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 (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