The Beginning of Science

The two years that he spent on Lesbos were perhaps Aristotle’s happiest. The island’s flora and fauna informed his theory of the form, which in turn informed his entire physics and metaphysics.

Aristotle remained at Plato’s Academy for nearly twenty years, only leaving after Plato’s death in 347. The reasons for his departure are unclear: he may have felt slighted at being passed over for the scholarchship of the Academy in favour of Plato’s nephew, Speussipus; or he may have fled, possibly even before Plato’s death, for fear of the growing anti-Macedonian feeling. In 351, the orator Demosthenes had delivered his First Philippic denouncing Philip II’s imperial ambitions, and in 348, the year before Plato’s death, Philip had razed Athenian ally Olynthus to the ground.

Then in his thirty-seventh year, Aristotle travelled with fellow Platonist Xenocrates of Chalcedon to Assos (in the Troad, Asia Minor) to join the court of Hermias of Atarneus, who had studied at the Academy. Aristotle may or may not have gone to Assos as an ambassador of Philip, who wished to have Hermias for an ally. In either case, it seems that he exerted a moderating influence on Hermias, who softened his harsh tyrannical rule—enabling him, in short succession, to win over neighbouring peoples and expand his territory.

In 344, Hermias was captured by a mercenary in the service of Artaxerxes III of Persia and tortured for information about the invasion plans of his ally Philip. But Hermias held his silence, his dying words being that he had done nothing shameful or unworthy of philosophy. Aristotle honoured the memory of his perfect friend with a statue at Delphi and a still extant hymn to virtue. At around this time, he married Hermias’ niece and adoptive daughter, Pythias, who helped him in his work and bore him a daughter, also Pythias.

After the death of Hermias, Aristotle and his student Tyrtamus crossed over to Lesbos to research the flora and fauna of the island and its remarkable lagoon, then known as the Pyrrha lagoon, now known as the Gulf of Kalloni. Tyrtamus went down in history as Theophrastus [‘Divinely-speaking’], the nickname given to him by Aristotle. Supposedly, the more empirical Theophrastus concentrated on the flora while the more speculative Aristotle concentrated on the fauna, so that the one is remembered as the father of botany and the other as the father of zoology. In fact, Theophrastus also wrote on animals, and Aristotle on plants, but these works have been lost, as have almost all of Theophrastus’ wide-ranging works.

Aristotle’s Biological Works

Aristotle’s biological works represent the first systematic study of biology and reveal a great deal about the man and his method. These works are usually ignored, though they make up a quarter of his extant corpus, and were revered by naturalists such as Georges Cuvier and Charles Darwin—who, in the year of his death, 1882, wrote to William Ogle that ‘although Linnaeus and Cuvier have been my two gods … they were mere schoolboys to old Aristotle.’

Although Linnaeus and Cuvier have been my two gods … they were mere schoolboys to old Aristotle. —Charles Darwin

Aristotle accompanied his History of Animals (a somewhat misleading title, cf. ‘natural history’) with a now lost book of anatomical drawings. His other biological writings are the Parts of Animals, Movement of Animals, Progression of Animals, and Generation of Animals, as well as On the Soul and seven shorter works collectively known as the Parva Naturalia.

On the Soul may seem out of place, until one remembers that the very word ‘animal’ [anima] means ‘having breath’ or ‘having soul’. The soul, says Aristotle, is the principle of life, and the knowledge of it contributes greatly to our understanding of nature and truth in general. On the Soul includes a detailed discussion of the senses and established our notion of the ‘five senses’, with Aristotle explicitly stating that ‘there is no sixth sense in addition to the five enumerated’.

On the Soul includes a detailed discussion of the senses and established our notion of the ‘five senses’, with Aristotle explicitly stating that ‘there is no sixth sense in addition to the five enumerated’.

In his biological works, Aristotle outlines more than five hundred species, some in more detail than others. He describes the chambered stomachs of ruminants, the social organization of bees, and the embryological development of a chick. He notices that some sharks are viviparous, and that whales and dolphins differ from other fish in breathing air and suckling their young. He infers that brood size decreases with body mass, whereas gestation period, and overall lifespan, increases. In a playful by the way, he remarks that ‘after drinking wine, the Indian parrot becomes more saucy than ever’.

For centuries, some of Aristotle’s accounts seemed too fanciful to be true, for instance, that the young of a dogfish grow inside their mother’s body, that the male of the river catfish guards the eggs for forty or fifty days after the female has left, or that male octopuses have a sperm-transferring tentacle that sometimes snaps off during mating. Each of these wonders of the world had to wait until the nineteenth century to be confirmed.

Unlike Plato, Aristotle privileged observation over speculation. Like our scientists, he began with a systematic gathering of data, from which he attempted to infer explanations and make predictions. He carried out dissections and even rudimentary experiments such as cutting out the heart of a turtle to discover that it could still move its limbs for a surprisingly long time.

However, he did not carry out anything like modern case-control studies, and relied uncritically on the lay testimony of beekeepers, fishermen, travellers, and the like. His lack of rigour led to some embarrassing errors, such as the claim that lions copulate back-to-back, while bears adopt the missionary position and hedgehogs stand on their hind legs to face each other. Or the claim that the female of several species has fewer teeth than the male. Among these species, he included humans, when he could simply have looked into Pythias’ mouth (wife or daughter).

Aristotle’s lack of rigour led to some embarrassing errors, such as the claim that lions copulate back-to-back, while bears adopt the missionary position and hedgehogs stand on their hind legs to face each other.

Biology as Philosophy

Aristotle was not simply doing biology for the sake of biology, but for the sake of philosophy. Like Plato, he was searching for universals, but this time from the ground up. ‘We should’ he said, ‘venture on the study of every kind of animal without distaste; for each and all will reveal to us something natural and something beautiful.’ 

An animal gives birth to the same animal because of its form [eidos] or ordering pattern—an idea that resonates with modern genetics. The male supplies the form, which is also the soul, in his semen, while the female provides the material in her menses. When the semen meets the menses, they congeal into an egg or embryo ‘like fig juice which curdles milk’. If the semen fails to ‘master the menses’, a female is born. The soul is not superadded or even supervenient, but corresponds to the animal’s ordering pattern and dynamic processes. Aristotle’s interest in biology informs his theory of the form, which in turn informs his entire physics and metaphysics.

Aristotle’s interest in biology informs his theory of the form, which in turn informs his entire physics and metaphysics.

All beings, from minerals to plants and animals, have a form, the potential of which determines their position on the eleven-rung scala naturae,or great chain of being. The Church adapted the concept of a great chain of being, which later helped to justify slavery, colonization, and evangelization. Plants have a vegetative soul, capable of growth and reproduction. Animals, as well as a vegetative soul, have a sensitive soul, capable of sensation and movement, and hence of desire and imagination. Humans, uniquely, also have a rational soul, capable of thought and reflection. Contra Plato, the soul inheres in the organism, and dies with it—except for the rational soul, which, being a part of God, is immortal. Thought cannot die, since, unlike all else, it is not the function of a particular organ—the brain and the lungs being, in Aristotle’s view, mere radiators for the heart, which is the site of the internal fire and the seat of intelligence, motion, and sensation.

Although he held that all beings have a form, and that the form is injected by the male (a male being defined as ‘an animal that breeds inside another’), Aristotle also believed that many lower animals spontaneously generate: that eels grow out of mud, and insect maggots from putrefying flesh, even though Homer had said otherwise—when, in Iliad XIX, Achilles fears that flies will ‘breed worms’ in the corpse of Patroclus. To be fair to Aristotle, he had observed that eels have no gonads, and could hardly have guessed that they only develop them in the course of their epic migration to the Sargasso Sea. The earliest challenge to spontaneous generation came as late as 1668, when Francesco Redi covered jars of rotting flesh with gauze and found that only the controls, that is, the uncovered jars, grew maggots.

Aristotle was not a Darwinist nor even a Creationist, but an eternalist who believed that the plants and animals before him had always existed and would always exist. One argument that he gives for eternalism is that, if motion had a beginning, this beginning must itself have resulted from a movement, which is a paradox. Although he privileged observation over theory, his eternalism, albeit logically held, blinded him to the significance of the petrified forest of Lesbos, which would have confronted him with fossilized trees from millions of years ago.

Such are the main lines of Aristotle’s biology and associated philosophy. Many of his inferences have not stood the test of time. Salacious animals do not age more quickly than continent ones. Hair is not grown at the expense of semen, even if women and eunuchs don’t grow bald. And it is not because they lack fatness that bloodless animals are shorter lived than sanguineous ones.

But was the beginning of science not bound to look like this? And is it not remarkable that we today can still read its record?

Aristotle spent no more than two years on Lesbos. In 343, King Philip commissioned him to tutor his son Alexander, who was then around thirteen years old, promising in return to rebuild his native Stageira and repatriate its former citizens.

Neel Burton is author of The Gang of Three: Socrates, Plato, Aristotle and How to Think Like Plato and Speak Like Cicero.