I was recently invited to speak at a medical conference in Athens on innovation in ancient Greek medicine. It seems an obvious title to speak about: Aristotle in the fourth century BC is credited with creating botanical and zoological science (my namesake Armand Marie Leroi’s 2015 book The Lagoon is subtitled How Aristotle Invented Science), and a century before Aristotle the elusive figure of Hippocrates lent his name to medical innovations (mostly preserved in the voluminous writings of the AD second-century physician and polymath Galen) that were to influence physicians’ ideas and practices for over 2,000 years.

The most significant innovation attributed to Hippocrates, who is often called ‘the Father of Medicine’, was his insistence on empirical observation of disease and treatments. The emphasis on a practical, observational approach to health is generally taken to have been a marked departure from earlier approaches evidenced in Greece and elsewhere in the ancient world, which included such practices as prayer, magic and incantations, the employment of medicinal herbs of unproven efficacy, and the inflicting of surgery, cautery, and incisions on un-anaesthetised patients.

However, the notion of ‘innovation’ in relation to Hippocrates raises several distinct ironies. First of all, although Hippocrates undoubtedly existed, no secure biographical information about him survives. Instead, his name stands for a collective (and not always uniform) approach to medical thought and practice represented by the ‘Hippocratic Corpus’, a compilation of around 60 treatises on medicine composed by a variety of authors over the fifth and fourth centuries BC, with titles including The Art of Medicine, Ancient Medicine, The Sacred Disease (epilepsy), Diet, Joints, Fractures, and Women’s Diseases. These texts evince different medical opinions and practices, though they generally reflect a common empirical spirit. For instance, the treatise The Sacred Disease rejects the common understanding of epilepsy as a god-sent condition: ‘the so-called Sacred Disease’, we read, ‘is no more supernatural or sacred than any other, but has its explanation in nature (physis)’.

The most vivid examples of this rationalising approach are found in the Epidemics. Hundreds of case histories are preserved in seven Hippocratic books under that name (Epidemiai simply means ‘visits’). They record how physicians visiting sick patients carefully observe such things as their age, gender, diet, habits, environments and emotional states. Symptoms such as fever, skin conditions, and respiratory irregularities are noted, and bodily fluids and irregular growths are scrutinised. Such observations enabled doctors to form diagnoses and, more importantly, to offer treatment plans (mainly consisting of diet, rest, and exercise) as well as prognoses (predictions of future outcomes for the patient) based on observational evidence rather than guesswork.

Sometimes, however, there was no time or opportunity for treatment and prognosis. Most case histories in the Epidemics are long and detailed, but a notably brief one describes the case of Crito of Thasos:

Seized with violent pain in the big toe during a walk.

Went to bed the same day: shivering, nausea.

Regained some warmth, at night was delirious.

Day 2: swelling of the whole foot, rather red about the ankle and distended.

Black blisters; acute fever; delirium.

Intestinal discharge thick, bilious, fairly frequent.

Died on the second day after onset.

Strikingly, the author describes the developing symptoms but fails to offer an intervention that can affect the course of events. Crito’s death after two days is recorded with bald factuality. This is typical of the Hippocratic approach: often a physician can only observe and report the course of the disease. Such honesty constituted a remarkable innovation in a society that generally shunned failure, and in a discipline whose practitioners needed to claim expertise (even if only in rhetorical terms) to ensure their status, reputation, and livelihood.

A second irony relating to the notion of innovation in ancient medicine is that the notion (to kainon in Greek) is explicitly repudiated in the Hippocratic Corpus. Rather reminiscent of the judge of the dancing competition in the 1992 film Strictly Ballroom who growls ‘There are no new steps’, the Hippocratic author of Ancient Medicine begins his treatise with an insistence that no new medical theory is required:

People who speak or write about medicine as based on elements of hot, cold, wet, dry etc. reduce the causation of human disease and death to a narrow range by postulating a small group of elements and the same ones for all conditions. They are clearly misguided… Medicine needs no new principle.

The reluctance to embrace untested theory was not a rejection of progress. Without the methods of systematic experimentation that modern science relies on, medical ideas were tested directly on human patients, often with a high risk to their health – as in the case of the ‘tossing ladder’ devised to treat hunchback, a novelty that was said to have drawn enthusiastic crowds. In a prescientific world, innovation had to be treated with caution.

While medical theories were acknowledged to be arbitrary, accurate forms of inquiry were potentially probative. The author of Ancient Medicine is confident about the ultimate success of cumulative observation:

The field of medicine has long existed, and a principle and method have been found whereby numerous sound discoveries have been made over an extended period. The remainder will be discovered if competent inquirers au fait with past discoveries use these as the starting-point of their investigations.

But in a further irony, this empirical foundation gave rise to the most enduring and potentially restrictive of medical theories, that of the humours. Humoral theory posits that the body’s health depends on the balance of four bodily fluids: blood, phlegm, yellow bile, and black bile. This was to become the cornerstone of medical practice for nearly two millennia. Physicians across medieval Europe and the Arab world sought to diagnose and treat illness by restoring balance among the humours; even as genuine scientific methods advanced, medicine remained shackled to this model.

The emphasis on balance derived not from observation of bodies but from Greek speculative philosophy. The early fifth-century thinker Empedocles had proposed that the universe was governed by two forces: Love (Philia), which brings things together, and Strife (Neikos), which pulls them apart, and that these forces operate on the four ‘roots’ of the cosmos – earth, fire, air and water. This theory is reflected in the words of the physician Eryximachus, a speaker in Plato’s Symposium (c. 385 BC), who describes both love and medicine in terms of harmony and balance: ‘In medicine, it is Love that reconciles opposites at war with one another such as cold and hot, bitter and sweet, dry and wet.’ The doctrine of balance left little room for further innovation until the Scientific Revolution provided new tools to observe and experiment with the human body.

Nonetheless, the detailed observations recorded in Hippocratic texts formed the basis of medical education for centuries. During the Hellenistic era (third to second centuries BC) major advances were made in Alexandria. The physicians Herophilus and Erasistratus conducted the first systematic dissections of human bodies and made discoveries about the nervous system. Herophilus distinguished between sensory and motor nerves, and was the first to describe the ventricles of the brain, while Erasistratus put anatomy and physiology on a sound footing. Galen was to reiterate the importance of empirical observation and the use of patient histories to develop personalised treatments. His own work on anatomy and physiology remained influential for centuries.

The understanding of health as involving balance, the rejection of untested theories, and the reliance on empirical evidence are threads that connect ancient and modern medicine and that continue to offer a point of departure for medical advances. The most well-known legacy of the Hippocratic Corpus, however, is the Oath, the symbol of medical ethics. Ancient physicians were made to swear to uphold strict ethical standards: above all to do no harm, but also to be discerning about what kind of treatment to apply, to act within the limits of their expertise, and to preserve patient confidentiality. These ideas were revolutionary in their time in creating an ethical basis for medicine as a profession rather than simply as a practice that relied on traditional folk remedies, persuasive arguments, and arbitrary theories of health and disease. The principles of the Oath remain the bedrock of medical ethics, even while modern science and technology allow for genuine medical innovations of a kind that Hippocrates and his school could never have dreamed of.