Herman Boerhaave was born in Voorhout on 31 December 1668. He was the first son of the Reformed pastor Jacobus Boerhaave and his wife Hagar Daalders. Boerhaave’s father destined his son for the church and therefore he himself started to teach the young Herman Greek, Latin, history and the New Testament. In 1682, due to a painful ulcer on his left thigh, Boerhaave moved to Leiden in order to get medical treatment. Eventually, however, Boerhaave successfully cured himself with a mixture of salt and his own urine. In Leiden he entered the third class of the Latin grammar school after which, at the age of fifteen, he moved on to the University of Leiden in order to study philosophy and theology. By that time his father had passed away and Boerhaave depended on a scholarship made available by the States of Holland for the training of clergymen.
On the recommendation of Jacobus Trigland Jr and Daniel van Alphen Simonszoon, Boerhaave became a pupil of Wolferd Senguerd , who taught him ‘dialectics, metaphysics, the use of the globes, and politics’, as Boerhaave wrote in his autobiographical notes. Under the supervision of Senguerd, Boerhaave held four public disputations; one on cohesion and three on the human mind. In 1687, Boerhaave became interested in mathematics. He studied geometry, and trigonometry, and their applications to algebra; he found these subjects ‘wonderfully agreeable to his talents’. Possibly Boerhaave also attended demonstrations in Burchard de Volder’s laboratorium physicum. In 1689, he held his first academic oration, on Cicero’s right understanding of Epicurus’s doctrine concerning the greatest good. For this oration he was awarded a gold medal.
Upon finishing his studies of philosophy in 1690 with a disputation on the mind-body dichotomy, defended under the supervision of De Voider, Boerhaave started reading medicine in 1691. Apart from attending anatomical dissections by Anton Nuck, Boerhaave was selftaught in medicine. He began his studies by reading the work of Hippocrates, advancing in chronological order through the medical authors until Thomas Sydenham ‘whom he worked through several times, each time more eagerly’, as Boerhaave himself observed. As his scholarship had run out, Boerhaave supported himself with what he earned from teaching mathematics privately and from keeping a supervisory post in the University Library.
In 1693 he went for his examination and graduation at the University of Harderwijk. Shortly afterwards Boerhaave was accused of having Spinozist sympathies, which, at the time, implied that he had an atheist inclination. This was occasioned by a mere question of Boerhaave, overhearing some people who were talking ignorantly about the philosophy of Spinoza , whether they had actually ever read any of Spinoza’s works. Although it is far from certain that Boerhaave’s thought was deeply indebted to Spinoza’s philosophy – it has been argued that due to his teacher De Volder he was influenced by the geometrical structure of Spinoza’s Ethics – this rumour greatly damaged his chance of earning a living in the Church, so that Boerhaave devoted himself wholly to a career in medicine. Until 1701 he lived a quiet life in Leiden. He began visiting patients and continued his studies in mathematics, physics, anatomy, chemistry and botany.
The year 1701 marks the beginning of Boerhaave’s teaching career, bringing fame to Boerhaave himself as well as to the University of Leiden. He was appointed lecturer in medicine; and with an oration in which he recommended the study of Hippocrates he took up his office. Privately Boerhaave also started lecturing on anatomy, chemistry, and practical medicine. Boerhaave’s teaching not only attracted many students from home and abroad, but also the attention of the Curators of the University of Groningen and the University of Franeker. Although he would not change to another university, the Leiden Curators decided to increase his salary and they promised him the first vacant chair. To mark the agreement Boerhaave delivered an address on the usefulness of the mechanical method in medicine (1703).
After the death of Peter Hotton in 1709, the curators fulfilled their promise and appointed Boerhaave to the chair of medicine and botany. His inaugural oration on the simplicity of purified medicine marks Boerhaave’s lifelong motto: simplex veri sigillum, simplicity is the sign of truth. In 1718, Boerhaave was also made professor of chemistry. With an address on ‘chemistry purging itself of its own errors’, he followed Jacobus le Mort to the chair. Meanwhile, after the death of Govard Bidloo in 1713, Boerhaave had also embarked on a clinical lecture course (collegium medico-practicum) in the Caecilia Hospital. At the height of his career, he was so busy that eventually his health was affected. In 1729 he decided to resign from his professorships in botany and chemistry. Boerhaave died on 23 September 1738, leaving his wife Maria Drolenvaux and his only surviving daughter Joanna Maria. His achievements for the university were many; he significantly enriched the botanical garden and improved the chemical laboratory; his textbooks in medicine, botany, and chemistry were translated into many languages and widely used in the Netherlands and abroad; his pupils took his method of teaching to other universities, most notably to Edinburgh, Göttingen and Vienna; he edited the works of Eustachius (1707), Vesalius (1725) and Swammerdam (1737); and he left behind an extensive correspondence with natural philosophers all over Europe.
During his life Boerhaave received many honours. He was twice awarded the office of Rector Magnificus of the University. In 1714 he commenced his office with a discourse on the achievement of certainty in physics and in 1730 he delivered an academic address on servitude as the physician’s glory. In 1714 Boerhaave was honoured with the chair of the Leiden Surgeon’s Guild. Boerhaave’s fame also spread abroad as he received royal visits from Czar Peter the Great and Prince Eugene de Savoy. He was elected foreign corresponding member of the Académie Royale des Sciences in Paris in 1715 and Fellow of the Royal Society of London in 1730.
It is impossible to assign Boerhaave’s ideas to one particular philosophical current, although contemporaries and historians have done their best to do so. For instance Julien Offray de La Mettrie, who published the first biography of Boerhaave in 1740, made Boerhaave a forerunner of his own materialism; and historians of science and medicine have often argued that Boerhaave presented a thoroughly mechanistic medicine, without appealing to vitalistic principles. Yet Boerhaave’s ideas changed over time, and cannot be summarized as materialistic or mechanistic.
In his early career, under the influence of Senguerd’s and De Volder’s teaching, Boerhaave addressed Cartesian topics. In 1687 he discussed cohesion, but rather than attributing cohesion to the size, shape and motion of particles only, as Descartes had done, Boerhaave acknowledged the existence of occult qualities which Descartes meant to exclude. Boerhaave’s other student disputations on the human mind have a more definite Cartesian ring. The body, so Boerhaave argued, is extended or impenetrable. The mind, on the other hand, transcends the material level of the body since it can think about immaterial objects, like universal truths, God, axioms, virtues and mathematical truths. Throughout his career Boerhaave maintained that the body is separate from the mind, although he also allowed for a connection, which he described as a harmony established by God. It is apparent that Boerhaave’s ideas on the mind-body connection have a certain Leibnizian ring, but in his writings there is no evidence of a direct influence of Leibniz’s philosophy on Boerhaave.
When Boerhaave started teaching medicine in 1701 he presented a medicine based on Cartesian mechanics and Newtonian hydraulics and hydrostatics. This is particularly visible in his 1703 oration on the usefulness of the mechanical method in medicine, where, following the suggestion of De Volder, he presented a mechanistic medicine. Everything in the human body works according to the laws of mechanics, he said, pointing in particular to the structure and organisation of the body’s tubes and vessels for the maintenance of life. Boerhaave’s mechanistic medicine is optimistic. Using the metaphor of a clock he explained that once the inner mechanisms of the body are known, the physician can correct its structure and repair defects.
In his 1709 oration on the simplicity of purified medicine Boerhaave moved away from the kind of medicine that was mainly based on mechanical principles. Instead he began emphasizing the individual powers of particles and bodies. As a result he no longer solely adhered to the mechanical philosophy, but he also turned to chemistry: for chemistry, in his view, was best able to analyse the constituent parts and powers of natural bodies. In his oration of 1715, on the question of certainty in physics, Boerhaave’s changing ideas are most clearly expressed. He argued against the Cartesians who defined bodies in terms of extension alone. He also denied that the concepts of empty space, the monad, and the gravity of bodies are of any use in understanding the nature of things. Alternatively he observed that the only things visible to the natural philosopher are the effects of nonmechanical causes, while the first principles of things always remain hidden. Hence, Boerhaave opposed all philosophers who set out to unravel the laws of nature in order to predict the course of nature with mathematical precision. According to Boerhaave, physicists and physicians can only investigate the simple powers of bodies, ‘but as soon as they attempted to take these as a starting point for setting laws to which all bodies would be subject, they erred most shamefully’.
The works of Newton had a decisive influence on Boerhaave’s mind. It cannot be a coincidence that shortly after the publication of Newton’s Opticks (1704 and particularly after the English edition of 1706), with its many references to the forces of attraction, and chemistry as a way to examine them, Boerhaave started devoting attention to the individual powers of bodies. However, while Newton and the Newtonians still aimed at the formulation of universal rules in order to understand the divine order, Boerhaave emphasized the powers peculiar to different natural bodies in particular situations. In his 1715 oration Boerhaave even ridiculed those natural philosophers who proclaimed attraction to be the first principle of all things. According to Boerhaave, the principles of motion, the elements and seminal principles, more than the Newtonian forces of attraction, reveal the rich variety in nature. He therefore turned to chemistry, for he argued that the changes of bodies effected by motion ‘is the subject of chemistry, and of chemistry alone’, and not of mechanics.
The chemistry Boerhaave presented was, so he stated, purged of errors and based on true principles. In his 1718 oration on the errors of chemistry being corrected by the chemists themselves, Boerhaave argued that the chemistry of his time was haunted by two major faults. First, many contemporary chemists and alchemists had invented their results. Secondly, in their longing for gold and riches, (al)chemists had erroneously used biblical texts in their chemical claims. In so doing they had turned the teachings of the Bible into maxims of alchemy. Following the approach of Bacon and Boyle, Boerhaave referred to experiment and observation in order to wipe out these errors. He particularly stressed the importance of understanding chemical experiment rather than following a set of prescriptions. This pedagogical aim permeates the whole of Boerhaave’s teaching. In clinical medicine, Boerhaave invited his students to diagnose illnesses themselves, while he supervised their doings. In chemistry likewise, Boerhaave encouraged his listeners not to blindly follow formulae, but to try to grasp what chemistry is about. The educational, rather than prescriptive character of Boerhaave’s chemistry made it unique among contemporaries. Hence, Peter Shaw called his English translation of Boerhaave’s Elementa chemiae, ‘A New Method of Chemistry’.
Boerhaave characterized matter as ‘inert’ and ‘passive’. His ultimate simple corpuscles resemble Newton’s smallest particles. The activity of nature, according to Boerhaave, happens in the pores between the particles. Motion itself, in Boerhaave’s view, must be derived from another metaphysical entity, i.e. God, who continuously infuses motion into matter. Since Boerhaave thought it impossible to obtain knowledge of the original and pure principles of matter, he therefore concentrated on knowledge of the principles of motion and change. He did not want to confine natural phenomena to general laws of nature. Rather he emphasized the importance of looking at the most simple powers peculiar to individual bodies, also including the so-called ‘occult qualities’. He argued that man should not shy away from seemingly miraculous appearances, but rather investigate their effects. Consequently Boerhaave did not shy away from alchemy. On the contrary, he praised the old alchemists (among them Geber, and in later years also Paracelsus and Johan Baptist van Helmont ) for their diligence and honesty in investigating the unknown properties of bodies, and he tried to improve their experiments on the metals.
In his later career, Boerhaave devoted much attention to the originally Stoic concept of ‘seminal principles’. In so doing he addressed a popular topic in seventeenth century atomism and chemistry. Boerhaave argued that seminal principles are the formative principles, ‘the foundation and support for each single body existing’, including the human body. Boerhaave even stated that, since all natural bodies depend on the seminal principles for their existence, all phenomena arising from the working of the seminal principles are the prime concern of the natural philosopher.
In medicine, as in chemistry and botany, Boerhaave stressed that the physician has to follow nature as his sole guide. He viewed the body as a circle without beginning or end in which the organs subsist and function harmoniously. No organ, in Boerhaave’s view, is worth more than another, so he denied the traditional opinion that the heart is the most important part of the body. In 1730, Boerhaave even named the body ‘the true image of the perpetuum mobile so long sought after’. Boerhaave set the works of Hippocrates and Sydenham as an example, for they had based their medicine upon the true principles of nature. The solid parts of the body are most important in Boerhaave’s medicine. He even reduced the motion of the fluids to the working of their smallest particles. Yet, the elementary particles themselves are unchangeable. In particular in his later career he emphasized the working of their ‘latent peculiar powers’ which determine the working of the body. For instance, when blood is too thin, this is not caused by the blood particles themselves, but by the forces of cohesion not working properly. Boerhaave argued that chemistry, rather than mechanics and physics, brings out the latent forces of bodies, which, in Boerhaave’s view, makes chemistry ‘surpass other disciplines in usefulness’ and indispensable to medicine.
Boerhaave’s botany mostly stood in the service of medicine and chemistry. His main botanical merit is the assistance and stimulus he gave to other botanists, like William Sherard, Sébastien Vaillant and Linnaeus . Although Boerhaave saw the need for a botanical classification, he was eclectic in his division of plants, combining the systems of Paulus Hermann and J.P. de Tournefort.
Although Boerhaave in his teaching closely collaborated with his colleagues in the faculty of philosophy (see his pupils Oosterdijk Schacht and Du Bois, in particular), little is known about the philosophical motivations shaping his work. Boerhaave has been generally viewed as one of the great eighteenth-century systematizers, who managed to transform a heap of philosophical, medical, chemical and other literature into a coherent rational system. Historians of science and medicine have also acknowledged an eclecticism in the philosophical premises of his work. In the process of systematizing, however, Boerhaave had some guiding principles informing his decisions. Recently, it has been pointed out that some particular philosophical and theological motivations are behind Boerhaave’s intellectual endeavours.
An irenic longing for peace of mind seems to be central to his teaching. According to the Commentariolus, a collection of notes in his hand on his life and family, which were found after his death, Boerhaave was appalled by the bitter differences of opinion of philosophers and metaphysicians on the meaning of the Scriptures. These disagreements, according to Boerhaave, had led to ‘passionate disputes, and hatred and ambition’. Yet the Bible, in Boerhaave’s view, speaks in an unambiguous way and ‘the teaching expressed by Jesus Christ… gives peace of mind’. The desire for peace of mind might be a key to understanding Boerhaave’s medicine. In the same way that Boerhaave referred the theologians back to the Bible, he also referred physicians to the works of Hippocrates as the basic core set of truths. From there one should read forward, always avoiding conflict. Irenic themes are visible in all Boerhaave’s orations, so his medical approach might have been aimed at promoting peace in medical science and among physicians.
The relation between Boerhaave’s theology and medicine may perhaps be only indirect. Although tranquillity of mind was a chief goal for him, Boerhaave was not a theological irenic, but rejected doctrine in favour of experience. Moreover Boerhaave’s medical system is not based on purely rational principles but on sense experience; and his classifications are based on external appearances. Boerhaave’s rejection of reason must be seen in the context of the philosophical discussions on reason and the passions in The Netherlands at the time. At the beginning of his academic career Boerhaave defended the neo-Stoic position that reason has to overcome the passions rather than indulging in them; in later years, perhaps as a result of reading Descartes’s Traité des passions de l’ âme (1649), he started doubting the capability of reason to check the passions. In medicine Boerhaave also moved away from reason. Due to his gradual rejection of the ability to know first causes through the method of reasoning, in medicine he confined himself to mechanistic explanations based on experiment and observation and no longer referred to the temperament and circumstances of every individual patient. Instead he stressed the ‘universal’ corporeal basis of health and disease. Boerhaave accordingly no longer ‘rationally’ counselled his patients on how to live better, but turned to ‘objective’ healing methods based on experiment and observation. It would be unwise, however, to emphasize this ideal of objectivity and to attempt to transform Boerhaave into an Enlightenment thinker. If we focus merely on Boerhaave’s medicine we might neglect ideas alien to modern science.
In order to judge Boerhaave’s significance for the history of philosophy it might be necessary to asses the influence of the Calvinism of his youth and of his theological studies on his later work in natural philosophy. Notwithstanding his mechanistic medicine, Calvinism accounts for Boerhaave’s great interest in latent forces and ‘occult’ powers. Two Calvinist themes are particularly evident in his work. First, Boerhaave aimed at showing the wisdom of God in the divine works of creation and providence. Second, the Calvinist emphasis on the fallen state of the human intellect and hence man’s inability to arrive at true knowledge is visible in all Boerhaave’s later writings. According to Boerhaave the immaterial and occult forces of bodies show the active hand of God in nature, while at the same time experiment and observation keep man from trying to understand the infinity of the divine. Boerhaave therefore put great emphasis on particulars rather than on general theory, for in the details of nature he could see God’s active government over creation. Moreover, the individuality of natural phenomena made him realise that trying to understand the works of God via the (Cartesian) method of mathematical reasoning was not only too ambitious, but entirely impossible. Boerhaave considered God’s divine works too great and too complex to fit into the limited enclosure of the human mind.
, ‘Medicine to Calm the Mind: Boerhaave’s Medical System and Why it was Adopted in Edinburgh' , in A. Cunningham and R. French (eds), The Medical Enlightenment of the Eighteenth Century (Cambridge, 1990), pp. 40–66 .
, ‘Herman Boerhaave (1668–1738) oder Spinozismus als rein mechanische Wissenschaft des Menschen' , in H. Delf von Wolzogen (ed.), Spinoza in der Europäischen Geistesgeschichte (Berlin, 1994), pp. 75–93 .
, ‘Mechanicisme contra Vitalisme: De School van Herman Boerhaave en de Beginselen van het Leven' , Gewina. Tijdschrift voor de Geschiedenis der Geneeskunde, Natuurwetenschappen, Wiskunde en Techniek , vol. 5 (1982), pp. 16–26.