Hahnemann and Leonardo da Vinci —Observation, Experiment & Experience

Written by Peter Morrell

Historian Peter Morrell discusses the parallels between Hahnemann and Leonardo daVinci in their philosophical leaning and approach to problem solving.  He also compares the philosophies of Darwin, Harvey, Newton and other inventive and creative thinkers.

“Galen, the ruler of men’s minds on all matters connected with medical science for thirteen centuries and more; his authority at once a despotism and a religion, which it would have been treason to question and impiety to gainsay; his works, with those of Aristotle, the text on which the intelligence of Europe expended itself in criticism and comment during all these ages.” (1)

First published in The American Homeopath –  Vol 24 -2018

To draw a parallel between Hahnemann (1755-1843) and Leonardo da Vinci (1452-1519) might seem a tad audacious or even bizarre, as they seem poles apart and to have been very different kinds of people. However, there are some important similarities where they come close, most especially in their attitude towards how real knowledge can be created.

Hahnemann can be successfully compared to several key figures in history such as Lord Francis Bacon (1561-1626), Galileo (1564-1642), William Harvey (1578-1657), Isaac Newton (1642-1727) and Charles Darwin (1809-1882), because they each in their day set their compass against orthodox views by declaring startling new discoveries and carving out new paths towards knowledge gained largely through empirical observation and experiment. And Hahnemann followed a very similar path.

They each regarded “reading the great book of nature,” (2) as a superior path to true knowledge rather than devotion to the dead hand of rigid scholasticism. For, “without observations and repeated experiments, the mind is only chasing after phantoms and appearances without any scientific value.” (3) In this respect, and each in their own way, they observed and interpreted things in ways that challenged the entrenched orthodox notions of the day and this rendered them rebels and iconoclasts, and therefore frontiersmen: pioneers of new knowledge. Also like Hahnemann they all had an excellent education and enjoyed high professional standing after studying at some of the finest European universities.


By strong contrast, Leonardo was the illegitimate son of an obscure peasant girl and had little or no formal schooling to speak of. His illegitimacy barred him from studying Greek and Latin and he spent his childhood exploring nature and pursuing his passion for drawing rather than studying books. \

He thus remained largely oblivious of the views and ideas of the great thinkers of the past. He never went to university and seemed to be quite scornful of the formal book learning of others. This attitude is shown where he says: “though I may not, like them, be able to quote other authors, I shall rely on that which is much greater and more worthy:—on experience, the mistress of their Masters.” (4) And also: “they do not know that my subjects are to be dealt with by experience rather than by words and [experience] has been the mistress of those who wrote well. And so, as mistress, I will cite her in all cases.” (5)

Astonishingly also, Leonardo predates by about a century all the key figures of the scientific revolution including Bacon. He pioneered the detailed exploration of natural forms and mechanisms as revealed through the anatomical and engineering drawings that fill his many notebooks.

Therefore, in the history of ideas he actually predates and foreshadows the empirical and observational methods of the great pioneers of science: Bacon, Galileo, Newton and Harvey. Yet he is rarely credited with that position perhaps because this aspect of the man has been obscured by his considerable artistic achievements.

His writings contain many examples of the value he places on experience:

  • “my intention is to consult experience first,” (6)
  • “my works are the issue of pure and simple experience, who is the one true mistress.” (7)
  • “sound rules are the issue of sound experience — the common mother of all the sciences and arts.” (8)
  • “Wisdom is the daughter of experience.” (9)
  • He relied on “nothing more than his considerable powers of observation and deductive reasoning.” (10) For example, his observations concerning the motion of waves in water, “laid the foundation for wave theory…and proposed that invisible sound waves travelled through the air in the same manner.” (11) Regarding his observation of the dual action of the biceps muscle, “it would be two centuries before Leonardo’s observation was repeated.” (12)
  • pure and simple experience, who is the one true mistress.” (13)
  • “good judgment is born of clear understanding, and a clear understanding comes of reasons derived from sound rules, and sound rules are the issue of sound experience—the common mother of all the sciences and arts.” (14)
  • “Certainly the proof should be allowed to rest on the verdict of experience.” (15)


In the 15th century, a number of Aristotle’s works were grouped together and called The Organon. The term means “instrument,” an instrument dealing with logic and for investigating the nature of truth. It sought to establish very clearly what we can say is true, and provided a series of guidelines on how to make sense of things.

For many centuries prior to Bacon the views of Aristotle had been revered as the absolute authority on philosophy and had been frozen into a strict orthodoxy until the birth of science in the early 1600s. (16)

Bacon’s Novum Organum, (publ. 1620) or The New Organon, rejected the dogmatic orthodoxy of Aristotle’s method and replaced it with the notion that real truths can only be discovered empirically from the observation of nature and by conducting experiments. (17) Bacon thus forms the obvious inspiration for those pioneers of science such as Galileo, William Harvey and Newton. (18)

Galileo was punished by the Church for teaching heretical views of planetary motion, (19) and Harvey was severely criticised for teaching his discoveries about the circulation of the blood that were contrary to accepted teachings. (20) Both were castigated as heretics for daring to publish views contrary to the accepted dogmas of Aristotelian thought i.e. the Church.

In both cases we see a clash between observation and received orthodoxy. In both cases we see people who admired the truth more than they admired orthodox dogmas and who then became portrayed as rebels and iconoclasts because of their adherence to the new truths they had unearthed.

They are both good exemplars of the empirical and experimental method which had been previously espoused by Bacon. However, what is also clear is that Leonardo was espousing and following the same empirical path for at least a century before Bacon.

Bacon is always credited as the originator of the experimental and empirical approach to obtaining truth because that is what he espoused in his Novum Organum and other writings. He is therefore rightly seen as the progenitor of the scientific method, as further refined by such figures as Descartes, and as employed by Galileo, Harvey and Newton and all the great scientists ever since.

In the Baconian view, any scientific theory should flow “naturally from observational data, not from holy writings or transcendental visions,” (21) and avoid any “unpleasant philosophical or theological conclusions.” (22) A truly scientific theory should justify “itself by reference to observational data…and not by invoking sacred texts or the mystical experiences of holy men…(it should emerge) straight from the observational evidence.” (23)

“Bacon’s is a theory about how to shape scientists (as they will subsequently come to be known), so that, contrary to their natural inclinations, they manifest the requisite good sense and behaviour in their observation and experiment.” (24)

The Baconian view does involve “a rejection of the classical tradition and an emphasis on many of the elements that Bacon will take up: above all, observation and experiment,” (25) and he did essentially argued for “an experimental science based on sensory observation.” (26)

However, Aristotle and the scholastics were not entirely wrong: “Aristotle realized (unlike almost everyone before him) that knowledge of nature requires systematic observation. Through careful examination he recognized an astounding amount of order within the living world, a crucial first step.” (27)

  • “Bacon’s overhaul of method was most properly construed by him to be a theoretical project – at stake in his project are the very grounds and enabling conditions of knowledge production, and the originary articulation, the invention in a sense, of the mechanisms — experience, experiment, induction, observation, etc. — by which this knowledge production is to be carried out.” (28)
  • “he follows only observations and sense experience,” (29)
  • “Bacon’s attempt to effect a fundamental reform of philosophy from a contemplative discipline exemplified in the individual persona of the moral philosopher, to a communal, if ultimately centrally directed, enterprise exemplified in the persona of the experimental natural philosopher. In turn, observation and experiment are lifted out of the purview of the arcane and the esoteric, and planted firmly in the public realm.” (30)
  • “there are significant Baconian precedents for…the idea of experiment and observation replacing Scholastic methods of disputation.” (31)
  • “Perhaps Bacon’s greatest influence on the seventeenth-century intellectual upheaval was his insistence on observation as the basis for knowledge of nature.” (32)
  • “Bacon’s chief complaint in connection with the false systems of natural philosophy was the methodology employed within those systems. He accused Aristotle of ‘bending’ experience to conform to his system. That is, rather than allowing nature to reveal itself as it actually is, Aristotle interpreted nature falsely in order to make it fit with his system. His snide remark at the end about the Scholastics reveals his belief that they followed Aristotle so uncritically, that they did not even check with experience to see if Aristotle’s system is empirically adequate. This led to a blind allegiance to a false system of natural philosophy, that is, to an Idol of the Theatre.” (33)


In agreeing with Copernicus mathematically that the sun is much more likely to form the centre of the solar system than the earth—because it gives a much more accurate account of the motions of the planets—Galileo set himself on a course towards conflict with the Church authorities.

He also bolstered his calculations with numerous actual observations of the heavenly bodies using a telescope. And yet, in spite of his close friendship with the Pope, his books were condemned as heretical, he was quizzed by the Inquisition and he then suffered house arrest for many years.

Galileo sets the precedent of a pattern of very negative reaction towards new ideas that was repeated by several other great thinkers and experimentalists. He has therefore become the martyr of the scientific approach and is still held up as a hero by the scientific community for being bold and daring enough to defy the received authority and immense power of the Church—a power often portrayed as a mindless form of authoritarian dogmatism.

Early science was “grounded not on tradition but its own observational and experimental processes, its own metaphysic, and its own philosophy of knowledge,” (34) and yet there had always existed an “empirical side of Aristotelian philosophy, stressing the importance of observation and experience in uncovering the secrets of nature.” (35) “It was by observation that solid knowledge of human anatomy had been built up since the early sixteenth century,” (36) which was then followed by a “vast expansion of scientific observation and experiments in the seventeenth century.” (37) This “new outlook upon nature was enriched and confirmed by zealous attention to observation and experiment.” (38)

Galileo’s telescope “had allowed him to see the mountains of the Moon and…by assiduous and painstaking observation he discovered four ‘stars’ that revolved around Jupiter,” (39) and “there can be no doubt that Galileo’s observation of the stars was the first step toward the universe of the vast numbers of stars and systems of stars at vast distances of modern cosmology.” (40)

However, the religious authorities would not readily “accept Galileo’s physical observations of the new celestial phenomena,” (41) and the Jesuits “either refused to believe the observations or sought ways of explaining away their troubling consequences.” (42)


Based on a series of ingenious experiments that he conducted on animals (mostly dogs, pigeons and deer), and the human arm, Harvey was able to demonstrate the absolute falsity of Galen’s 1500 year-old views about the circulation of the blood.

For example, he showed for the first time the clear differences between the arteries and veins, the direction of blood flow in each and the mathematical absurdity of Galen’s view that blood is synthesised in the liver from food, then pumped out from the heart to the tissues where it dissolves.

Harvey demonstrated that given the accurately measurable volume and beat of the heart it would be impossible in a 24 hour period for the body to synthesise the enormous volume of blood that Galen’s theory required.

“Galen mistakenly thought that blood was pumped out to irrigate the tissues, and that new blood was made continuously to resupply the heart. His idea was taught for nearly fifteen hundred years. It was not until the seventeenth century that an Englishman, William Harvey, introduced the theory that blood flows continuously in one direction, making a complete circuit and returning to the heart. Harvey calculated that if the heart pumps out just two ounces of blood per beat, at 72 beats per minute, in one hour it would have pumped 540 pounds of blood—triple the weight of a man! Since making that much blood in so short a time is clearly impossible, the blood had to be reused. Harvey’s logical reasoning (aided by the still-new Arabic numerals, which made calculating easy) in support of an unobservable activity was unprecedented; it set the stage for modern biological thought.” (43)

In fact, he demonstrated convincingly that the heart pumps the same volume of blood around the body over and over again, being carried out to the tissues by the arteries and then returned to the heart by the veins.

“He relied on experimentation, comparative anatomy and calculation to arrive at his conclusions…many proponents agreed with his theory largely because of the logic of his argument and his use of experimentation and quantitative methods. Many opposed the circulation theory because of their rigid commitment to ancient doctrines, the questionable utility of experimentation, the lack of proof that capillaries exist, and a failure to recognize the clinical applications of his theory.” (44)

However, his views were condemned as heretical, especially in Catholic southern Europe, where there were calls for his imprisonment and his books were condemned.

In England he was protected by his close association first with King James I and then with his son, King Charles I. “Harvey had been physician extraordinary to James I since 1618 and remained at court to attend Charles I after James died in 1625.” (45) “Harvey said that Charles I ‘much delighted in this kind of curiosity [the dissection of the organs of generation of deer] and was pleased many times to be an eye-witness to my discoveries’.” (46)

Regardless of his honesty and his ingenious experimentation, Harvey was for many years reticent and hesitated to share or publish his ideas, being fearful of the way they might be received as heretical teachings that he felt might (a) damage his reputation as an anatomist and physician, and (b) provoke losses to his medical practice.

These fears proved to be well-founded and some years of criticism would have to elapse before his teachings on blood circulation would be finally accepted into mainstream medicine.


Apart from his mathematical and religious writings, Isaac Newton is rightly famous for his investigations concerning gravity, optics and mechanical motion. For these developments he is recognised as one of the greatest scientific geniuses of all time.

However, he was also criticised—mostly by religious and artistic people—for creating a materialist, godless and mechanical view of the universe. For example, William Blake painted him as a dangerously satanic figure and condemned the Newtonian universe in the lines of a poem: ‘a robin redbreast in a cage sends all heaven into a rage.‘ (47)

Considering Newton’s own deeply-held religious views, this critique is a tad ironic. Blake was reacting not so much to Newton the man but to the godless and mechanical interpretation of his ideas that had become the scientific norm after his demise.

Blake regarded Newton as “trapped within the confinement of his own calculations,” (48) because he detested the idea that the universe is “governed by the immutable laws of the inverse square rule and the fluxional calculus…a vast machinery of order and uniformity.” (49) Blake “denounces Newton and Locke as the great enemies…he accuses them of seeking to imprison the free human spirit in constricting, intellectual machines.” (50) He thought that Newtonian physics “crushes the life out of the free, spontaneous, untrammelled human spirit.” (51)

Perhaps the ‘godless mechanical universe’ died out with Einstein and Schroedinger, and one imagines that today very few scientists (52) hold that firmly to such an idea; many would probably admit the possibility of the creative imagination, the free human spirit and even of religions and gods.

In that sense perhaps Blake had misread Newton. However, the accuracy with which objects can now be sent from earth to another planet and land within seconds or minutes of the predicted landing time is a powerful confirmation not only of Newton’s mechanics but also of his mathematics.


Charles Darwin made new sense of the fossil record and comparative anatomy through reference to variation and competition in populations, and so created a theory of evolution that totally outshone the simplistic notions of his French predecessor, Lamarck.

Darwin and Mendel are both rightly revered as heroes of the scientific method and for their construction of innovative and compelling theories about the natural world. Even Galileo and Harvey, who at the time were condemned as heretics by the Pope, were eventually recognized. All these great men are rightly seen as heroes of the scientific method.

There is no doubt that Harvey and Galileo paid a high price for their ‘heresy.’ Harvey must have been immensely grateful he was living in a Protestant country, for if he had still been living in Italy he would certainly have received a visit from the Inquisitors.

Bacon and Newton did not face the same opprobrium. Worst of all Darwin had attacked the very fabric and foundation of Victorian life: the Church. Apart from Bacon and Newton, they each paid the heavy price of seeing their professional standing tainted by their writings. Hahnemann likewise.

Darwin was driven into a neurotic state and became obsessed about his health problems for years, largely due to being wracked by guilt at the implications his theory would have for theology. He seems to have been struggling with his “God-implanted monitor, conscience.” (53)

To be regarded as a decent, moral and upright citizen in Victorian times required one to be seen to have an outlook supportive of the values of the Anglican Church. His faith had lapsed, he had stopped attending church and he was cognisant of the grave implications his writings would have on the otherwise high status he enjoyed in Victorian society. His theory of evolution was dismissed by the church as godless and materialistic and seemed to spell yet another scientific attack on Christian theology.


Darwin was not a mere theorist as he spent a lot of his time making observations of living things and also conducting numerous experiments. Darwin “rejoiced in the employment of his wonderful power of observation in the physiological problems which occupied so much of his later life.” (54)

His investigations and experiments chiefly involved worms, barnacles and plants. “The key empirical aspect of Darwin’s observation…remained constant from 1835.” (55) He conducted many experiments on cross fertilisation in flowering plants as well as others on the effect of light on growing seedlings.

He also conducted experiments on the survival rates of seeds in saltwater to test his theory that plants could spread their seeds perhaps over hundreds of miles of ocean. Regarding “Darwin’s scientific method…observation, close and detailed, was at the centre of his procedure. Such observation…was always accompanied by a stream of theory. As his son Francis remarked, “He often said that no one could be a good observer unless he was an active theoriser.” (56)

Therefore, it is fair to say he was an excellent observer, naturalist and experimental scientist in the mainstream sense. For example: “This was his most prodigious, painstaking series of experiments. The plants had to be protected from insects by sheets of gauze. He cross-fertilized some batches and selfed others. Seeds were carefully collected, labelled, and grown to maturity under identical conditions.” (57)


Hahnemann was beset by poverty nearly all his life and was really a very serious and conservative person – there wasn’t really very much joy in his life and he was consumed by a sense of duty and a sense of mission to do something important.

One does not get any of those impressions with Leonardo da Vinci, who seems by contrast to have been a far more flippant and carefree person who took his time and followed his own passions much more than any abiding or serious sense of mission.

Even his art – incredible though it is – was almost an accidental by-product of his love of life and his insatiable curiosity rather than stemming from any all-consuming or serious sense of mission. Innately, his life seems to have contained much more exuberant joy and love of life than Hahnemann’s.

Almost all Hahnemann’s writings are peppered with the word ‘experience’ and it is therefore very easy to find examples where he refers to the value he places on this quality. His work was “founded on premises derived from experience,” (58) and carved out “according to principles based on nature and experience.” (59) In Aphorism 6 of The Organon, he bemoans the, “futility of transcendental speculations which can receive no confirmation from experience.” (60)

His medical views were arrived at entirely through empirical experiment—”derived from pure experiences and observations,” (61) and “in consonance with nature and experience.” (62)

In aphorism 52 he affirms his medical knowledge derives from, “accurate observation of nature, on careful experimentation and pure experience.” (63) His views sprang from endeavour and hours of sober reflection as well as tireless experiment, what he himself calls: “many years of reflection, observation and experience.” (64)

Hahnemann “was a physician basing himself as far as possible on experience.” (65) His views were “based upon his own experiences.” (66) He enunciated “principle based purely upon experience and without questionable theories.” (67) Every time, and by deep instinct, “he will not devise and puzzle out anything by meditation but would go the way of pure experience.” (68) He “criticizes general medicine, its uncertainty and the views built upon insufficient experience and the speculations in medicine.” (69) Consequently, “he treasures pure medical experience,” (69) claiming that “there is knowledge only in the domain of sensory experience, metaphysics as a science is impossible.” (70)

All his views amount to “prudent conclusions built of experience.” (71) He denies absolutely that there is any value in endless medical speculation: “in every pure experiment and every true experience, the fact is consequently established; it matters but little what may be the scientific explanation of how it takes place.” (72)

In his construction of homeopathy, Hahnemann gives “pure experiment, careful observation and accurate experience alone,” (73) as the sole determining factors, the sole forces that shaped his new system. Hahnemann “cast tradition aside, and had recourse only to the medicines he had learned, tested and confirmed.” (74) “Hahnemann developed his theory not on the basis of speculation, but as the result of pure observation.” (75) Hahnemann regarded the theories of allopathy as “constructions of the intellect, something that was not found but made…an enormous fallacy,” (76) because he held that true knowledge of medicine “was not to be acquired from authority, but existed in the natural objects themselves.” (77)

Like Paracelsus before him, Hahnemann “thought he could learn more medicine by travelling and observing than from any library,” (78) and, like William Harvey, Hahnemann professed to learn “not from books…not from the tenets of Philosophers, but from the fabric of Nature.” (79)

As far as Hahnemann was concerned, “physiology…looked only through the spectacles of hypothetical conceits, gross mechanical explanations, and pretensions to systems…little has been added…what are we to think of a science, the operations of which are founded upon perhapses and blind chance?” (80) He condemned “speculative refinements, arbitrary axioms…dogmatic assumptions…(and the) magnificent conjuring games of so-called theoretical medicine.” (81

Hahnemann had little time for “medical pedantry,” (82) and the “dogmatic demand of exclusive devotion to one method.” (83) In effect, the average doctor of Hahnemann’s day was “bound in the fetters of dogmatic assertion, he stumbled through life, trying to plant his uncertain feet in the footsteps of those he accepted as his masters; preferring that his patient should die according to rule rather than be cured by unauthorized measures; and opposing heresy more vigorously than he opposed disease.” (84)

Hahnemann denounced their use of “hypothesis, explanations, demonstrations, conjectures, dogmas and systems whose consequences were then apparent.” (85)

He regarded the medicine of his day as having chiefly “evolved out of physicians’ heads, out of illusion and caprice,” (86) and of comprising “an infinite kingdom of fantasy and of arbitrary assumptions, the parent of disastrous delusion and of absolute nothingness.” (87)

It seemed merely to spring from “irrational principles,” (88) and to exemplify “the vain impotence of our art.” (89) ) In all these points he makes clear that he values observation and experience above every kind of theoretical speculation or rational deduction.

He makes it clear that he has turned his back on theoretical medicine as taught by university professors, which he dismisses as vain and useless. He always places method and experience absolutely above ideas and theories. And in this regard he shows just how close he has come to the same views of Leonardo, Harvey and Bacon.

In the 5th Organon Hahnemann uses three words a great deal. These words are: experience, observation and experiment. He uses experience 82 times, observation appears 46 times and experiment appears 65 times. I believe these figures speak volumes about the true origins of homeopathy as a medical science. They show just how firmly homeopathy was rooted in observation, experiments and experience—the very watch-words of all the mainstream sciences.


Hahnemann probably comes closest to Galileo and Harvey in terms of the strong negative reaction that greeted his ideas. In all three cases one might say the new ideas were too radical and far-reaching to evoke even a whisper of public acceptance.

In all three cases also, what was being proposed amounted to the outright rejection of an entire paradigm and its replacement with something strangely new and unfamiliar. In all three cases the new ideas threatened to overturn many centuries of entrenched dogmas.

The reaction from the establishment in all three cases was broadly similar: so-called heretical teachings were attacked and denounced and the person espousing them identified, targeted, ostracised and subjected to very uncomfortable public and professional pressures and restrictions.

The Church presented a pretty united front against the ideas and publications of Galileo. And the professors of medicine presented a united front against Hahnemann just as they had done against Harvey. This form of professional behaviour or closing of ranks is typical whenever the accepted ideas and practices of a profession are attacked or rejected from within.

The problems Hahnemann had from the apothecaries and fellow physicians differ very little from the reactions of senior clerics to Galileo and the professors of medicine to Harvey. In such cases, the offending ‘heretic’ is denounced publicly, their ideas rejected and colleagues are encouraged to join in with other acts of very public condemnation.

Newton and Bacon did not receive any of these types of treatment but Darwin did. One might say that Newton had merely made discoveries that did not overthrow a paradigm but which mostly added new material to established knowledge of the physical world in a way and at a time that was not totally challenging to the accepted world order.

Darwin’s ideas, however, did amount to an order-changing set of new doctrines that shook society to its core. Clearly, the most shocking logical conclusion of his work was that humans are basically little more than animals that had evolved from ape-like ancestors.

This was deeply challenging to the accepted religious ideas of the day, which regarded human beings as special, as distinct from and superior to the animal world and the product of divine creation.

For him to suggest that anatomically we are so little different from the apes amounted to an outrageous proposition at the time. There is no doubt that he knew in advance that his conclusions about evolution would place him on a personal—and very uncomfortable—collision course with the Church and that this knowledge cautioned him to delay publication as long as possible.

He grew fearful of the negative effect publication would have on his reputation as a respected scientist and country gentleman of good standing in Victorian society. This reaction based on foreknowledge was broadly similar to Harvey, who also delayed publication of his ideas for about 11 years.

When we compare Hahnemann with Leonardo it seems the comparison breaks down in terms of how they fared in society. Or does it? Leonardo was not ostracised and denounced by his colleagues as a dangerous revolutionary, rebel and heretic in the way Hahnemann was.

In fact he was lauded as a painter of great genius. Perhaps this reflects a difference between the world of art and that of medicine? In 15th century art there were well-established rules to follow but if the end product was stunning, then the innovative methods were neither questioned nor condemned.

In early 19th century medicine, by contrast, that was simply not the case. The difference with art would seem to be that the normal methods and rules had never coalesced into a set of rigid dogmas backed up by Aristotle—as they certainly had in medicine—and so when a new style came along it may have been scorned, but the artist was not treated as a pariah.

In the cases of Galileo, Harvey and Hahnemann, the methods and rules which they ‘broke’ had been crystallised into dogmas for many centuries and strict adherence to them was policed with fanatical zeal. In any case Leonardo’s methods mostly amounted to little more than very skilful refinements of techniques already in use.

Although one might choose to regard the ideas of Hahnemann, Harvey and Galileo, as mere modifications and refinements of previous work, such a view was rarely expressed at the time. Indeed, their proposals amounted to a revolution in ideas that could not be easily tolerated.

To sum up about Leonardo and Hahnemann we can include the following features that they both seemed to have in common:

  • great attention to detail
  • learn from and praises experience
  • praises empirical study
  • exceptional observational powers
  • great skill
  • artistic ability
  • conducted experiments
  • hard work – a grafter
  • freethinkers
  • truth comes first
  • dismissive of authority
  • led more by evidence than by dogma
  • both prefer practice over theory

Leonardo predates Bacon but essentially espoused the same advice about observation and experiment, while Hahnemann preached the very same idea and followed the same method as Bacon, Leonardo, Galileo, Harvey and Darwin.

He used the word experience much more than the rest but in essence it means the same thing: close observation, attention to detail, experiment and endless trial and error. It all boils down to finding things out for yourself rather than following books and experts. Of course the major difference between Hahnemann and Leonardo concerns their education and their attitude towards educated people.

Hahnemann is not alone in using three words a great deal. We find the same words crop up with similar regularity in Leonardo’s Notebooks, and in Isaacson’s biography of Leonardo.

Word Organon 5 Isaacson Leonardo Notebooks
Observation 46 74 54
Experience 82 38 53
Experiment 65 101 47


This is where they come so close. They both relied heavily on trial and error, observation and experimentation, one in the honing of their artistic skills and the other in formulating a new system of medicine. The parallel doesn’t end there.

When Hahnemann translated the Thesaurus medicaminum in 1800 he wrote a preface and in it he said “the best counsel I can give you, dear reader, is to place the main body of this book into the fire.” (90) The Thesaurus medicaminum was no trifling book, it was a thick tome, a classic work on Materia Medica of the time, detailing every drug in use, its properties and the doses physicians should use for them all.

This was a standard work which he translated into a text of 412 pages. Why then should Hahnemann recommend that the reader should burn this book? A very simple answer: because he found it to be a useless work of fiction!

Through personal experience he had found that the drugs in it did not possess the properties listed and the doses had just been copied and recopied for centuries. This meant Hahnemann, in great despair, had reached the end of the road and abandoned medicine solely because the drugs in use did not do what the books and professors claimed. And it was that fact which set him on the path of proving medicines himself.

A major difference between Hahnemann and Leonardo is that Hahnemann had been taught a set of rules, an ‘instruction manual’ if you will all about how to practice medicine. Leonardo had never been given any such instruction manual; from childhood he was untutored, a blank canvas!

He had to work things out entirely as he went along driven solely by the insatiable curiosity and natural talent of this incredible man. He created his own instruction manuals for painting, for anatomy and for engineering as he went through life derived solely from his own observation, experimentation and experience.

Sadly for Hahnemann, the instruction manual he had been given by his teachers turned out to be useless. And so this very learned man—a man heavy and weighed down by his own learning—was forced to abandon all that learning, and create from scratch a new instruction manual for a new form of medicine.

That is basically what the Organon evolved into. In this regard he ended up in a similar place to where Leonardo had started out: working things out by trial and error as he went along. And in this endeavour—just like Leonardo—he relied heavily on the same three important qualities: observation, experimentation and experience. And these were the very same tools used and recommended by the great scientists we have looked at: Galileo, Bacon, Harvey, Newton and Darwin.


  1. Robert Willis, William Harvey: a History of the Discovery of the Circulation of the Blood, London: Kegan Paul, 1878, p.41
  2. M Sgarbi, The Aristotelian Tradition and the Rise of British Empiricism, Springer, 2013, p.91
  3. Sgarbi, op cit., p.183
  4. Leonardo da Vinci and Jean Paul Richter (trans.), The Notebooks of Leonardo Da Vinci, 1888, p.11; Walter Isaacson, Leonardo Da Vinci, Simon and Schuster, 2017, p.170
  5. Vinci & Richter, op cit., p.10
  6. Isaacson, op cit., p.173
  7. Isaacson, op cit.
  8. Isaacson, op cit.
  9. Vinci & Richter, op cit., p.1150
  10. Leonard Shlain, Leonardo’s Brain: Understanding Da Vinci’s Creative Genius, Lyons Press, 2015, p.116
  11. Shlain, op cit., p.118
  12. Martin Clayton & Ronald Philo, Leonardo Da Vinci: The Mechanics of Man, Getty Pub, 2010, p.38
  13. Vinci & Richter, op cit., p.12
  14. Vinci & Richter, op cit., p.18
  15. Vinci & Richter, op cit., p.654
  16. Ahmed Alwishah & Josh Haye, (Eds.) Aristotle and the Arabic Tradition, Cambridge: CUP, 2015, pp.2-3
  17. Francis Bacon, Lisa Jardine, Michael Silverthorne, Francis Bacon: The New Organon, Cambridge: CUP, 2008, p.5
  18. Walter Pagel, William Harvey’s Biological Ideas: Selected Aspects and Historical Background, Basel & New York: S Karger Publications, 1967, pp.344-48
  19. Stillman Drake, Galileo at Work: His Scientific Biography, New York: Dover Publications, 2003, p.349
  20. William Harvey, Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus, (An Anatomical Study of the Motion of the Heart and of the Blood in Animals), London, 1628; Thomas E Wright, William Harvey: A Life in Circulation, Oxford: Oxford University Press, 2013
  21. Michael J Behe, Darwin’s Black Box: the Biochemical Challenge to Evolution, Free Press, 2006, p.244
  22. Behe, op cit., p.245
  23. Behe, op cit., p.246
  24. Stephen Gaukroger, Francis Bacon and the Transformation of Early-Modern Philosophy, Cambridge: CUP, 2001r, p.12
  25. Gaukroger, op cit., p.14
  26. Dennis Desroches, Francis Bacon and the Limits of Scientific Knowledge, Continuum, 2006, p.58
  27. Behe, op cit., p.7
  28. Desroches, op cit., p.182
  29. Gaukroger, op cit., p.180
  30. Gaukroger, op cit., p.221
  31. Gaukroger, op cit., p.224
  32. K Hutchinson & S Gaukroger, The Uses of Antiquity: the Scientific Revolution and the Classical Tradition, Springer, 1991, p.145
  33. Laurence Carlin, The Empiricists: a Guide for the Perplexed, Continuum, 2009, pp.21-22
  34. A Rupert Hall, The Rise of Modern Science – from Galileo to Newton 1630-1720, New York: Harper & Row, 1963, p.35
  35. Peter Machamer, The Cambridge Companion to Galileo, CUP, 1998, p.38
  36. Hall, op cit., p.34
  37. Hall, op cit., p.27
  38. Hall, op cit., p.7
  39. Machamer, op cit., p.19
  40. Machamer, op cit., p.252
  41. Hall, op cit., p.22
  42. Machamer, op cit., p.247
  43. Behe, op cit., pp.7-8
  44. S A Lubitz, Early reactions to Harvey’s circulation theory: the impact on medicine, Mt Sinai J Med. 2004 Sep;71
  45. Roger French, William Harvey’s Natural Philosophy, Cambridge: Cambridge University Press, 1994, p.114
  46. French, 1994, p.339
  47. See Kevin Hutchings, Imagining Nature: Blake’s Environmental Poetics, McGill-Queen’s University Press, 2003, p.53; Kathleen Raine, Blake and Tradition, Princeton University Press, 1968, p.49
  48. Peter Ackroyd, Blake, London: Vintage Books, 1996, p.193
  49. Ackroyd, p.193
  50. Isaiah Berlin, The Proper Study of Mankind, London: Pimlico, 1998, p.259
  51. Berlin, op cit., p.260
  52. For example, Richard Dawkins. See: Amit Goswami, God Is Not Dead: What Quantum Physics Tells Us about Our Origins and How We Should Live, Hampton Roads Publishing Company, 2012, pp.9-10, p.34, p.136; Graham Smetham, Quantum Path to Enlightenment, lulu.com, 2017, pp.13, 217, 264, 296; David Ludwig, A Pluralist Theory of the Mind, Springer, 2015
  53. Samuel Hahnemann, Contrast of the Old and the New Systems of Medicine, Reine Arznthnittellehre, part iv, 2d edit. 1825, reprinted in R E Dudgeon (Ed.), Hahnemann’s Lesser Writings, London, 1852, pp.712-723, p.719
  54. A C Seward, Darwin and Modern Science: Essays in Commemoration of the Centenary of the Birth of Charles Darwin, CUP, 1909, p.385
  55. Sandra Herbert, Charles Darwin, Geologist, Cornell Univ Press, 2005, p.315
  56. Philip Pomper, David Gary Shaw (eds.), The Return of Science: Evolution, History, and Theory, Rowman & Littlefield Publishers, 2002, p.61
  57. A Desmond and J Moore, Darwin, London: Michael Joseph, 1991, p.775
  58. Samuel Hahnemann, The Organon of Medicine, combined 5th/6th Edition, Translated by R.E. Dudgeon, and edited by William Boericke, Philadelphia: Boericke & Tafel, 1893, §28
  59. Organon §5, footnote
  60. Organon, p.32
  61. Organon, Preface to 2nd Edition
  62. Organon, Introduction
  63. Organon, §52
  64. Organon, §205
  65. Rudolf Tischner, History of Homeopathy (trans. L J Boyd), New York: AIH, 1933, p.167
  66. Tischner, op cit., p.170
  67. Tischner, op cit., p.176
  68. Tischner, op cit., p.245
  69. Tischner, op cit., p.270
  70. Tischner, op cit., p.315
  71. Tischner, op cit., p.316
  72. Organon, §28, quoted in Tischner, p.319
  73. Martin Gumpert, Hahnemann – The Adventurous Career of a Medical Rebel, New York: L B Fischer Publ. Corp., translated from the German by Claude W Sykes, 1945, p.144
  74. Gumpert, op cit., p.67
  75. Edward C. Whitmont, Psyche and Substance: Essays on Homeopathy in the Light of Jungian Psychology, Berkeley, California: North Atlantic Books, 1980, p.40), p.40
  76. Isaiah Berlin, ‘Georges Sorel’ in Against the Current: Essays in the History of Ideas, London: Pimlico, 1979, p.298-302; pp.301-2
  77. Roger French, Medicine before Science: the Business of Medicine from the Middle Ages to the Enlightenment, Cambridge: Cambridge University Press, 2003, p.149
  78. French, 2003, op cit., p.148
  79. Roy Porter, The Greatest Benefit to Mankind A Medical History of Humanity, New York: Norton, 1998, p.215
  80. S Hahnemann, Aesculapius in the Balance, 1805, in Lesser Writings, pp.410-434; pp.423-6
  81. Wilhelm Ameke, History of Homœopathy, with an appendix on the present state of University medicine, translated by A. E. Drysdale, edited by R. E. Dudgeon, London: E. Gould & Son, 1885, p.134
  82. Linn J Boyd, A Study of the Simile in Medicine, Philadelphia: Boericke & Tafel, 1936, p.125
  83. Boyd, op cit., p.9
  84. C T Campbell, Personality of Hahnemann, Cleveland Ohio: Hahnemann Society, 1892, p.8
  85. Boyd, op cit., p.70
  86. Ameke, op cit., p.134
  87. Ameke, op cit., p.134
  88. Organon 5, §104
  89. Hahnemann, 1805, op cit., p.415
  90. Robert E Dudgeon, Lectures on the Theory and Practice of Homeopathy, London & Manchester: Henry Turner & Co, 1853, pp.xxvii-xxviii

About the author

Peter Morrell

Peter Morrell is a medical historian and freelance researcher. He completed an MPhil thesis on the history of British homeopathy in 1998 and was Hon Research Associate at Staffordshire University (1999-2009). He has published many articles on the history of homeopathy and the life of Hahnemann. In recent years his research has focused increasingly on the Casebooks of Hahnemann's medical practice. Peter graduated in zoology from Leeds University and has taught life sciences since 1975, mostly in colleges in the UK. You can find many of Peter Morrell's excellent articles here: http://www.homeoint.org/ morrell/articles/index.htm

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