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Yearly Archives: 2011

Hypotheses versus theories

Peter Anstey writes…

Chapter 5 of William Poole’s The World Makers (Peter Lang, 2010) opens with a very interesting epigraph from the Cambridge antiquarian Thomas Baker’s Reflections on Learning (1699):

    But we have been taught to distinguish betwixt Hypotheses and Theories, the latter of which are shrew’d things, as being built upon Observations in Nature, whereas hypotheses may be only Chymaeras: I should be glad to see that Theory, that is built upon such Observations …  (p. 82)

While Poole doesn’t mention the connection, this distinction almost certainly derives from William Wotton’s precursor to Baker’s book, namely, Reflections upon Ancient and Modern Learning (London, 1694). There, Wotton claims:

    In judging of Modern Discoveries, one is nicely to distinguish between Hypothesis and Theory. (p. 235) … And therefore, that it may not be thought that I mistake every plausible Notion of a witty Philosopher for a new Discovery of Nature, I must desire that my former Distinction between Hypotheses and Theories may be remembered. I do not here reckon the several Hypotheses of Des Cartes, Gassendi, or Hobbes, as Acquisitions to real Knowledge, since they may only be Chimaera’s and amusing Notions, fit to entertain working Heads. I only alledge such Doctrines as are raised upon faithful Experiments, and nice Observations; and such Consequences as are the immediate Results of, and manifest Corollaries drawn from, these Experiments and Observations: Which is what is commonly meant by Theories. (p. 244)

This hypothesis–theory distinction seems to be of Wotton’s own making. It is an effective means of dealing with the problem of the utility of hypotheses in a climate in which the notion of hypothesis was, to say the least, on the nose. Wotton spouts the standard anti-hypothetical rhetoric – the hypotheses of Descartes and others are mere chimeras ­­– but he is not insensitive to the fact that experiments and observations on their own are not sufficient for the advancing of true explanations.

Wotton was not an experimental philosopher. Rather, his Reflections was written as a defence of modern learning, and, in particular, the experimental philosophy, in the battle of the books. His comments and those of Baker, are therefore, indicative of the reach of the methodological stance of experimental philosophy beyond the writings of natural philosophers themselves.




Experimental vs Speculative Philosophy in Early Modern Italy

Alberto Vanzo writes…

So far, we have argued in many posts that British philosophers from the 1660s onwards worked in the tradition of experimental philosophy and criticized speculative philosophy. However, the distinction between experimental and speculative philosophy was also widely employed outside the British isles. In this post, I will document the presence of the experimental-speculative distinction in Italian natural philosophy between 1667 and 1716.

The Accademia del Cimento, founded by 1657 by Prince Leopoldo de Medici in Florence, was one of the first scientific societies in Europe. In 1667 the Accademia published a collection of experimental reports with the title Saggi di naturali esperienze. The preface to this work ends with a caveat:

    We would not like anyone to believe that we presume to give to the light a complete work, or even only a perfect scheme of a great experimental history, because we know well that more time and strengths are required for such an enterprise […] if, sometimes, an even minimal allusion to anything speculative has been made, […] always take it to be a specific idea or intuition of [some] academics, but never one of the Accademia, whose only aim is to experiment and to narrate.

Note the emphasis on experiments, the references to natural histories, and the refrain from endorsing any speculation. These are all indications that the Academy was presenting its work in terms of the then nascent distinction between experimental and speculative philosophy.

Not everyone was endorsing experimental philosophy in late seventeenth-century Italy. However, some of the authors who expressed reservations towards it did so in terms of the experimental-speculative distinction. For instance, Daniello Bartoli distinguished in 1677

    the two manners of natural philosophy which nowadays are very rumored, because they fight over the glory of primacy […]: the Theoretical and the Experimental […]

On the one hand, theoretical or “purely speculative” philosophy “needs experimental [philosophy] to “see [things] by means of the senses”. On the other hand, “purely experimental” philosophy must seek the help of speculative philosophy to proceed from particular experiences to their causes.

    [E]ither [philosophy], by itself, can be defeated if the other does not help and rescue it when it may fall down. But if both are united and if they fight side by side, although they may not always win, surely they will never be defeated.

Among the Aristotelians, Giovanni Battista de Benedictis (writing under the pseudonym of Benedetto Aletino) criticized experimental philosophy for its inability to proceed from facts to causes. He claimed that experimenters were not philosophers, but mere empirics, because they failed to establish any evident, undisputed premises as the basis for a deductive scientia of nature.

    Indeed, if our Peripatetics, who only paid attention to speculative subtleties, had followed Aristotle’s teachings by directing their efforts towards experience, I have no doubt that they would have unfailingly attained the glory that the Atomists [i.e., experimental philosophers] are now seizing, not because of their knowledge, but because of the neglicence of others [the Peripetetics].

While Aletino defends the Aristotelians, he categorizes them as speculative philosophers and he rejects experimental philosophy.

Antonio Conti was a Venetian abbot who acted as intermediary in the epistolary exchange between Leibniz and Newton. He published a discussion of the relation between experimental and speculative philosophy in 1716. For Conti, experimental philosophy alone “is truly science” because it rely on experience to prove the truth of its claims. By contrast, speculative or conjectural philosophy can only establish the probability or truth-likeliness of hypotheses. Due to the endless variety of nature and the limitations of our senses, Conti did not think that experimental philosophy could eventually supplant all speculations. His fallibilism concerning hypotheses sounds rather modern:

    One makes hypotheses to establish [new] ideas and experiences; but hypotheses last only until phenomena modify or destroy them, or until a more perfect art of comparing truth-likely [statements] proves their uselessness or their imprudence.

Like Bartoli, Conti endorsed experimental philosophy without wholly rejecting the speculative approach. Bartoli and Conti, like Aletino and the compiler of the Saggi di naturali esperienze, thought of natural philosophy in terms of the experimental-speculative distinction. As in the British isles, so also in Italy the experimental-speculative distinction provided important terms of reference for thinking about nature in the late seventeenth and early eighteenth centuries.

In this post, I have not discussed to what extent the experimental-speculative distinction shaped the contents, besides the rhetoric and methodology, of Italian natural philosophy. I must do more work to answer that question. In the meanwhile, let me know what you think in the comments.

Hooke’s Knowledge of Optics

This is a guest post by Ian Lawson.

Robert Hooke knew how light worked. He worked with the stuff day in day out during the early 1660s and in Observation IX of his Micrographia (1665) he presents quite a systematic theory of optics.

He presents his theory as the result of a startling observation about the colours of the rainbow observable in thin sheets of muscovy glass (mica). This observation he takes to be an ‘experimentum crucis’ against Descartes’ optical theory, ‘serving as a Guide or Land-mark, by which to direct our course in the search after the true cause of Colours’ (Micrographia, p. 54). His positive thesis starts by outlining a hypothesis about light based on some widely accepted principles (though I won’t go into the details here). This hypothesis he checks against more evidence, this time a glass globe filled with water. He finds his idea consistent with the phenomenon, while Descartes is again lacking. An ‘instantia crucis‘ this time – a sure sign he’s on the right track (ibid., p. 59).

A schema from the Micrographia

To refine his theory, Hooke continues experimenting. Now he uses water in a long glass tube and sheets of muscovy glass split to varying thicknesses. He adds detail until he feels he can account for all kinds of colour phenomena. ‘By this Hypothesis there is no one experiment of colour that I have yet met with, but may be, I conceive, very rationally solv’d, and perhaps, had I time to examine several particulars requisite to the demonstration of it, I might prove it more than probable…’ (ibid., p. 69).

Hooke presents his theory in an ordered and structured way. First he disproves the leading existing theory, then puts forward his own hypothesis. He returns to experiment to check factual adequacy, and uses further trials to refine the general idea. Focusing on his theory as it is presented, though, makes several features of his account mysterious. Why is it tacked on to the end of an observation about colours in a mineral? Why should colour even be the main part of an optical theory? And given that it is, why does he never mention prisms?

Hooke's experimental apparatus

Hooke's apparatus

What is worth noting is the experiments and observations Hooke makes. There are four primary apparatus he uses:

1. Muscovy glass

2. Glass lenses with water between them

3. Water globes

4. Glass vials filled with water.

Prisms, that paradigmatic optical experimentation device used by Descartes, Boyle, Power, and Newton in their experimenting about colour, are conspicuous by their absence. Rather, all of the experiments mentioned by Hooke are, in fact, part of his everyday set up for making microscopical observations. Numbers 2) and 4) are simply water microscopes, which he mentions using in the Preface to Micrographia. Number 3) is a scotoscope, used for concentrating light rays onto a small area to provide illumination, and also described in the Preface. And number 1) was Hooke’s preferred choice of microscope slide, as he explains when recounting his replication of Antoni van Leeuwenhoek’s observations in the late 1670s. It is unlikely that someone in possession of mica, ornate microscopes, and with connections among the fellows of the Royal Society as well as the instrument makers of London, was unable to obtain prisms with which to make experiments.

What is more likely is that, having spent four years making microscopical observations, Hooke stumbled again and again upon the incidental production of colours by his instruments. Chromatic aberration was a well known problem in microscopes and telescopes, which would not be solved until Dollond’s innovations in the eighteenth century. But using muscovy glass for specimen slides, and a water globe for illuminating his subjects, exposed Hooke two forms of colour production others may not have noticed. What’s more, in his Preface Hooke provides not only a detailed drawing of his primary instrument, but instructions on how it is made, and other versions suitable for other situations. Hooke doesn’t seem to have thought of his microscope as a static, finished product. Rather, he used one instrumental set up to make observations of distant objects such as the moon, and another to view things nearby and in his control. Even this could vary depending on whether the subject was translucent or opaque, and on the amount of light required to illuminate it. He notes trialling lenses made not just of glass, but resin, gum, oil, salt, and arsenic. All of this points to a man very aware of the behaviour of light and the process of refraction by which objects are magnified, and who was able to alter his instruments for the best results.

Hooke's microscope

Hooke's microscope

Some features of his theory are better explained by noting this likely route to Hooke’s knowledge of light, but a perhaps more difficult historical question is raised. Why did he present his observations as a constructed, systematic theory of colours rather than simply part of a history, as Boyle had done the previous year? It is likely the answer has something to do with ambition and rhetoric, and the role both Hooke and the other Fellows thought Micrographia would play in the early days of the Society.

Kant on experiments, hypotheses, and principles in natural philosophy

Alberto Vanzo writes…

As we have often noted on this blog, early modern experimental philosophers typically praised observations and experiments, while rejecting natural-philosophical hypotheses and assumptions not derived from experience. Along similar lines, Larry Laudan claimed that aversion to the method of hypothesis characterized “most scientists and epistemologists” from the 1720s to the end of the eighteenth century. Laudan mentioned Kant as one of the authors for whom “the method of hypothesis is fraught with difficulties”.

Immanuel Kant

Immanuel Kant

In this post, I will sketch a different reading of Kant. I will suggest that Kant, alongisde other German thinkers like von Haller, is an exception to the anti-hypothetical trend of the eighteenth century. Kant held that natural philosophers should embrace experiments and observations, but they are also allowed to formulate hypotheses and to rely on certain non-empirical assumptions. They should develop fruitful relationships between experiments and observations on the one hand, (some) hypotheses and speculations on the other.

I will illustrate Kant’s position by commenting on a sentence from the Pragmatic Anthropology: when we perform experiments,

    we must always first presuppose something here (begin with a hypothesis) from which to begin our course of investigation, and this must come about as a result of principles. (Ak. 7:223)

1. “[W]e must always first presuppose something here (begin with a hypothesis)…”

“For to venture forth blindly, trusting good luck until one stumbles over a stone and finds a piece of ore and subsequently a lode as well, is indeed bad advice for inquiry”. Even if we tried to perform experiments in a theoretical void, our activity would still be influenced by hypotheses and expectations. “Every man who makes experiments first makes hypotheses, in that he believes that this or that experiment will have these consequences” (24:889).

Like British experimental philosophers, Kant acknowledges that hypotheses and preliminary judgements may be “mere chimeras” (24:888), “romances” (24:220), castles in the air, or “empty fictions” (24:746). Hypotheses, like castles in the air, are fictions, but not all fictions must be rejected. The power of imagination, kept “under the strict oversight of reason” (A770/B798), can give rise to useful “heuristic fictions” (24:262). What is important is to be ready to reject or modify our hypotheses in the light of experimental results, so as to get closer and closer to the truth.

2. “…and this must come about as a result of principles.”

What principles are involved in our natural-philosophical investigations? As is well known, Kant holds that nature is constrained by a set of principles that we can establish a priori, like the causal law. In what follows, I will focus on three other principles that guide our experimental activity. They are the principles of homogeneity, specification, and affinity.

  • The principle of homogeneity states that “one should not multiply beginnings (principles) without necessity” (A652/B680). Kant takes it to mean that one must always search for higher genera for all the species that one knows. An example is the attempt to regard the distinction between acids and alkali “as merely a variety or varied expression of one and the same fundamental material” (A652-53/B680-81).
  • The principle of specification prohibits one from assuming that there are lowest species, that is, species which cannot in turn have sub-species. This led, for instance, to the discovery “[t]hat there are absorbent earths of different species (chalky earths and muriatic earths)” (A657/B685).
  • The principle of affinity derives from the combination of the principles of homogeneity and specification. It prompt us to look for intermediate specices between the species that we already know.

For Kant, the principles of homogeneity, specification, and affinity are not derived a posteriori from our experimental inquiries. They are a priori assumptions that guide them. We would not find higher genera, lower species, and intermediate species in the first place, unless we assumed that they exist and we tested that assumption with experiments and observations. For Kant, this is a non-empirical assumption that precedes and guides natural-philosophical inquiries. These do not unfold entirely a posteriori. They presuppose hypotheses and principles that are prior to experience and enable us to extend our knowledge of the world. Thus, rather than rejecting hypotheses and non-empirical assumptions as many experimental philosophers did, Kant holds that a guarded use of them is useful for our study of nature.

Miracles and ‘Experimental Theism’

Juan Gomez writes…

Greg Dawes pointed out to me a passage in David Hume’s Dialogues Concerning Natural Religion where we find the term ‘experimental theism.’ In this text, Hume seems to be referring to an argument given by one of the characters in the dialogue, Cleanthes, where the principle “like effects prove like causes” functions as a premise in an argument for a Deity. But what is really striking is that the term “experimental theism” nicely describes the approach George Turnbull takes in his religious texts, the Principles of Christian Philosophy (1749) and the earlier Philosophical Enquiry Concerning the Connexion Between the Doctrines and Miracles of Jesus Christ (1731). In this post I want to look at the earlier religious text and examine Turnbull’s exposition of what I believe is his ‘experimental theism’.

Turnbull constantly refers to the way natural philosophy is practised in order to adopt the same methods in inquiries into any kind of knowledge at all, whether moral or natural (see my previous posts here and here). His text on the Doctrines and Miracles of Jesus Christ is no exception. The interesting aspect of this text is that Turnbull draws an analogy between experiments and miracles. His argument begins by explaining how we come to know the laws of matter and motion:

    It is by experiment, that the natural philosopher shews the properties of the air, for example, or of any other body. That is, the philosopher shews certain effects which infer certain qualities: or in other words, he shews certain proper samples of the qualities he pretends the air, or any other body that he is reasoning about, hath. Thus is it we know bodies gravitate, attract, that the air is ponerous and elastic. Thus it is, in one word, we come to the knowledge of the properties of any body, and of the general laws of matter and motion.

This is the same way we can know if someone possesses a particular, skill, power, knowledge, or character:

    ’Tis by proper samples or experiments only of power and knowledge, that we can be assured, one actually possesses a certain power of knowledge. Just so it is only by samples or experiments, that we can judge of one’s honesty, benevolence, or good intention.

In the same way, “It is from the works of the Supreme Being, that we infer his infinite wisdom, power and goodness; as from so many samples and experiments, by which we may safely judge of the whole.” This is way of proving through ‘samples and experiments’ is what allows Turnbull to draw the connection between the Doctrines and the miracles. The miracles are sufficient proof of the doctrines, since they are the samples and experiments that show that Jesus has the set of powers entailed by the three kinds of doctrines of Christianity Turnbull identifies: the doctrine of future rewards and punishments, of resurrection of the dead, and of the forgiveness of sins.

Turnbull begins by examinig the doctrine of the resurrection of the dead. He tells us that Jesus has claimed that he has the power to raise the dead. How can we tell if this is the case or not? Well we need samples and experiments:

    It was necessary to give samples, or experiments, of this power he claimed. And accordingly he raised from the dead; and gave power to his apostles to raise from the dead. And to put his pretensions beyond all doubt, he himself submitted to death, that he might give an incontestible proof of his being actually possessed of that power, by rising himself from the dead the third day, according to his own prediction.

Within this theory, miracles are analogous to the experiments and facts that work as proof for theories about the natural world. Turnbull examines the other two kinds of doctrine in a similar manner and concludes that Jesus Christ has given proper proof of having the powers he has claimed to have, and as evidence Turnbull cites the many passages in the New Testament where we find anecdotes of the miracles performed by Jesus Christ. The analogy is further explained when Turnbull considers the fact that we cannot understand the nature of miracles. It is not necessary that we understand the nature of the miracle, since it is still proof of the power of performing such miracle. This is the case with attraction in natural philosophy:

    Attraction, say all the philosophers, is above our comprehension: they cannot explain how bodies attract: but experience or samples certainly prove that there is attraction. And proper experiments or samples, must equally prove the power of raising the dead, tho’ we do not understand, or cannot explain, that power.

There are many interesting aspects in Turnbull’s religious thought worth looking into, but for now I’ll leave you with the few snippets provided here. The most relevant feature of Turnbull’s explanation of miracles is that it shows how committed he was to applying the experimental method to any sort of inquiry. He did this in moral philosophy, and here he does it regarding religion. Besides the use of the rhetoric of the experimental philosophy and the consideration of miracles as experiments, he even concludes the text with a list of queries, providing us with some insight of what a work of ‘experimental Theism’ would look like.

The Giant’s Shoulders Blog Carnival #41

Welcome to the 41st edition of The Giant’s Shoulders blog carnival, a monthly roundup of the best blog posts on the history of science. We had a lot of great submissions this month – organized below in a few handy categories below for your reading pleasure.

Tales from the (science) crypt

Quite a few submissions for this edition of the carnival dealt with topics from the weird/occult with a scientific take on it. Eric Michael Johnson in The Primate Diaries tells us about the first anecdotes of vampires and how “they tell an important story about how people understood natural events.” Eric also gives us a post (first published at archy) about Stalin and his alleged plan to create an army of ape-warriors. The post focuses on the ethics of such type of scientific experiments.

The Witchfinder General, from a 1848 history of the Royal SocietY

We also received two submissions on curious topics found in the Royal Society’s Philosophical Transactions. Emma Davidson writes in the blog of the Royal Society’s History of Science Centre about “spooky subjects” in the Philosophical Transactions. In the traditional way of the members of the Royal Society, Davidson gives us samples of their approaches to witchcraft and ghostly themes. The other post in this area comes from the BBC News Magazine and it shows curious entries in the Royal Society’s archive, among them canine blood transfusion and a 1665 article about “the view from the moon.” Fascinating!

Finally, over at the blog of the Philadelphia Area Center for History of Science Darin Hayton looks at a controversy regarding the number of witches that were executed.

Historical figures

We received a number of great posts about interesting historical figures. At Providentia, Romeo Vitelli puzzles over the suicide of Ludwig Boltzmann in 1906: a man who had so much to live for! Tim Jones at Zoonomia tells us a few things he gleaned from Sir David Attenborough’s Darwin Lecture 2011 about Alfred Russel Wallace (co-discoverer of natural selection). He describes how Darwin and Wallace “reached a gentlemanly solution with no ill feelings all round”. Stephen Curry at Reciprocal Space tells us about Benjamin Thomson (a.k.a. Count von Rumford), who led the revolution against Lavoisier’s caloric theory of heat. He describes Rumford as “not a man wracked by self-doubt”, who had the audacity to draw a very flattering analogy between himself and Newton! Michael Ryan at Paleoblog tells us about Giovanni Arduino, the father of Italian geology, who gave a clear paleontological interpretation of the age sequence of the fossil record. Over at the Royal Society Blog, Emily Roberts tells us about the 16th-Century forebears of Boyle, Wren and Newton: John Rastell, Thomas Digges, John Dee, and William Gilbert. Finally, at Art History Today, David Packwood offers us an interesting portrait of Leonardo da Vinci as artist and natural philosopher.

Astronomy and space travel, past and present

Pluto looks at Pluto (from the Vintage Space blog)

Over at the Provientia blog, Romeo Vitelli gives us a fascinating account of John Wilkins’ early plans (as early as in 1638!) for a spaceship designed to take us to the Moon: “a flying machine, designed like a sailing ship but with clockwork gears and a set of wings. The wings would be covered with swan or goose feathers and would be powered by an internal combustion engine using gunpowder.”

At Vintage Space, Asteitel tells us the story of the rise and fall of Pluto: how it was discovered, how its anomalies were identified, until the International Astronomical Union established that it is not a planet in 2006 – unless you are in Illinois, where Pluto is a planet by law.


Syphilis was known as the morbus gallicus, but at Powered by Osteons, Kristina Killgrove tells us about newly discovered evidence for its presence in Roman Spain as early as the second or third century AD. “So did the Romans have syphilis? The jury’s still out, but I’m guessing there will be enough evidence soon for someone to add ‘insanity resulting from neurosyphilis’ to the list of crazy theories for why the Roman Empire fell.”

Moving to modern times, Jai Virdi explains how the aurist John Harrison Curtis used an instrument – the cephaloscope, on which he wrote a treatise in 1842 – to affirm his authority, as a symbol of skills and judgement. Speaking of authority, the Quack Doctor features an entertaining excerpt from a satire of itinerary eighteenth-century medical salesmen:

    Gentlemen, Because I present myself among you, I would not have you to think, I am any Upstart Glister-pipe Bum-peeping Apothecary; no, Gentlemen, I am no such person: I am a regular Physician, and have travelled most Kingdoms in the World, purely to do my Country good.
1902 eruption of Santa Maria

Eruption of Santa Maria (from Magma cum laude)


On the topic of geology, as well as the post on Giovanni Arduino, we received one from Jessica Ball at Magma cum Laude, where she discusses the 1902 eruption of Santa Maria. She looks at a particularly descriptive account of the eruption, explaining it in modern scientific terms. And David Bressan, over at History of Geology, tells us about the development of Ichnology (‘the examination of traces’), and the early forebears of this field – Leonardo da Vinci and Ulisse Aldrovandi – who drew some dangerous conclusions!


We were pleased to find some blog posts about or inspired by current exhibitions. Jacy Young has an entry on a very interesting film archive on the History of the Human Sciences. Kris Coronado gives us an account of an impressive collection of books (and a meteorite!) displayed at Johns Hopkins, first editions of both of Newton’s most famous works among the books exhibited. Katy Barrett reminds us in her post how those of us involved in research projects tend to take our particular questions wherever we go, when she tells us how an exhibition at the British Museum got her thinking about longitude. Last but not least, Laura Massey gives us a very interesting post on the advances of cryptography brought about by the Shakespeare authorship issue, theme of an upcoming movie called Anonymous.

That’s all for this edition of the Carnival. Thanks to all the bloggers for providing so much interesting reading material and to you, reader, for stopping by. The next edition of the Carnival is still looking for a home. If you would like to volunteer as a host, get in touch with Thony C or with the Dr SkySkull. Nominations as usual by the 15th December either directly to the host or on the Carnival website.

The Aims of Newton’s Natural Philosophy

Kirsten Walsh writes…

In a previous post I discussed the aim of absolute certainty in Newton’s early optical papers.  I argued that this aim provides the link between Newton’s mathematical and experimental methods.  This quest for certainty is an enduring feature of Newton’s natural philosophy, leading to a modest natural philosophical agenda.  For example, in the General Scholium to the Principia (1713), Newton writes:

    “I have not as yet been able to discover the reason for these properties of gravity from phenomena, and I do not feign hypotheses … And it is enough that gravity really exists and acts according to the laws that we have set forth and is sufficient to explain all the motions of the heavenly bodies and of our sea.”

But is this really enough, for Newton?  Apparently it’s not.  In the very next paragraph, Newton begins to speculate on the “subtle spirit” that permeates bodies and might be operative in various phenomena.  It looks like he is proposing a causal explanation of universal gravitation.  However, these speculations end before they really begin, when Newton concludes that “there is not a sufficient number of experiments to determine and demonstrate accurately the laws governing the actions of this spirit.”

This is the final line of Principia.  And, for such a controversial book, this is a rather inauspicious ending.  But I think we can glean something about the aims of Newton’s natural philosophy from this.

To begin, we need to distinguish between what Newton wants to achieve, and what he thinks he can achieve.  Newton wants to give a complete, true theory of the world – including an account of the motions of the planets, the cause of gravity, and even God’s relation to the natural world.  But, in the trade-off between completeness and truth, Newton sides with truth.  For, as he writes in an unpublished Preface to Principia (mid-1710s), “still it is better to add something to our knowledge day by day than to fill up men’s minds in advance with the preconceptions of hypotheses.”

Newton’s modesty and restraint should not be misinterpreted as lack of epistemic ambition.  The surest way to achieve absolute certainty would be to keep his domain of inquiry as narrow as possible.  But Newton doesn’t do this.  Instead, he pushes at the boundaries of what can be known with certainty.  This is demonstrated by his use of Baconian Induction to make increasingly general claims about gravity.  Newton ambitiously generalises from pendulums, to terrestrial bodies, to all bodies.  In an unpublished Preface to Principia, he writes:

    “But it has also been shown in the Principia that the precession of the equinoxes and the ebb and flow of the sea and the unequal motions of the moon and the orbits of comets and the perturbation of the orbit of Saturn by its gravity toward Jupiter follow from the same principles and what follows from these principles plainly agrees with the phenomena.”

So what do those final two paragraphs of the General Scholium tell us about the aims of Newton’s natural philosophy?  I. Bernard Cohen says that the General Scholium is similar to the discussions that are found in scientific papers today: Newton is discussing the implications of his results and suggesting areas of further research.  On this reading, Newton is saying that there are two jobs ahead:

  1. To give a causal explanation of gravity; and
  2. To apply the theory of gravity to other phenomena in order to solve other problems.

Importantly, Newton thinks that we can begin on (2) without waiting to complete (1).  This is why Newton says it is enough that he has established that gravity exists and acts according to certain laws.

Related Posts: Newton on Certainty, Newton’s 4th Rule for Natural Philosophy.

The origins of the modern meaning of ‘empiricism’

Peter Anstey writes…

It is often supposed that the term ‘empiricism’ in its Kantian sense would have been entirely foreign to philosophers of the early modern period. For, throughout the seventeenth century the term ‘empiric’ had pejorative connotations. When used in medical contexts it normally referred to quacks: medical practitioners who are untutored, but who have pretentions to therapeutic medicine on the basis of experience alone. By extension, the term came to mean imposter or charlatan.

Yet when used as a name in the plural, ‘empirici’, it often referred to those ancient physicians who relied on observation over theory in their therapeutic medicine. Needless to say, those physicians in the early modern period who were associated with the experimental philosophy affirmed this emphasis on observation. It is worth inquiring, therefore, as to whether the term ‘empiric’ was ever used in a positive sense and whether physicians were proud to be labeled empirics?

One early use of the term ‘Empericism’ is in the chymical physician George Starkey’s Nature’s Explication (1657). But Starkey uses the term pejoratively in criticizing the Galenists who relied too heavily on theory. He says:

    the Chymistry of the Galenical Tribe is a ridiculous pardy [sic.], and partly dangerous Empericism, in stead of so commendable a Method and Art, as they with confidence and impudence sufficient boast it to be (p. 245)

Here Starkey is inverting the charge normally laid at the feet of the chymical physicians, namely that they were untutored quacks. Starkey implies that the Galenists were untutored in the chymical arts.

Interestingly, however, just over a decade later, the chymical physician George Thomson, when defending the chymical physicians against the charge of being empirics (made by Henry Stubbe), picks up the positive connotation of ‘empirici’ and aligns the chymical physicians, including himself, with empirics in so far as they are the true experimental physicians. In his Misochemias Elenchos or, A Check given to the insolent Garrulity of Henry Stubbe … With an Assertion of Experimental Philosophy (London, 1671), Thomson says the following:

    We shall examine the Original derivation of the word Empiricik, which arises from peirazo vel peirao experior, vel exploro, to try, assay, or prove, to review or find out any thing by diligent searching: so then empericos is but an Experimental Physician, one of a Sect very well allowed of by the Ancients: … who as Celsus delivers hath acquired the knowledge of Physick only by Use and Experiments, so he treats of it, not able to give a Natural Cause thereof. … I wish ye would be so Ingenious as your Tutor, to confess the greatest knowledge ye have obtained in the Iatrical part of late, hath been delivered to you by such Empiricks as ye abusively nominate me (p. 5).

Thomson goes on to liken the chymical physicians to ‘the poor Experimental Chymical Samaritane, carrying some Balsamical Remedy about him, poureth it in with his own fingers, taking care of the Patient to purpose. Such an one I profess my self, but yet not an Empyrick according to H[enry] St[ubbe]’ (p. 6).

Here in a book defending experimental philosophy, just as we find 100 years later in a book from 1771 by the German physician Georg Zimmermann, the term ‘empiric’ is explicitly aligned with the experimental philosophy as applied in physic, that is, therapeutic medicine. This, in turn, is suggestive of the origins of the positive association of ‘empiricism’ with an emphasis on observation. It may also reveal something of the origins of Kant’s use of the terms ‘Empirismus’ and ‘Empiristen’ to refer to those who emphasize the acquisition of knowledge by observation and experiment.

Von Haller on hypotheses in natural philosophy

Alberto Vanzo writes…

Typically, the experimental philosophers on whom we focus in this blog promoted experiments and observations, while decrying hypotheses and system-building. This is the case for several experimental physicians, to some of whom we have devoted the last two posts. Their Swiss colleague Albrecht von Haller thought otherwise. He published an apology of hypotheses and systems in 1751.

Von Haller was a novelist, a poet, and an exceptionaly prolific writer on nearly all aspects of human knowledge. He is said to have contributed twelve thousand articles to the Göttingische gelehrte Anzeigen. However, von Haller was mainly employed as an anatomist, physiologist, and naturalist. Like his Scottish colleague Monro I, he had studied in Leyden under Boerhaave. Having achieved Europe-wide fame for his physiological and botanical discoveries, von Haller was called by George II of England, prince-elector of Hanover, to occupy the inaugural chair of medicine, anatomy, botany and surgery at the newly founded University of Göttingen. Göttingen was under the strong influence of British culture throughout the eighteenth century and would later be the main centre of German experimental philosophers. While in Göttingen, von Haller was mainly engaged in his physiological and botanical studies, besides organizing an anatomical theatre, a botanical garden, and other similar institutions.

Haller’s essay, entitled “On the Usefulness of Hypotheses”, was first published as a premise to the German edition of Buffon’s Natural History. It was reprinted posthumously in 1787. Throughout these years, several authors in the German speaking-world endorsed Newton’s radically negative attitude towards hypotheses. For instance, few years after von Haller’s essay the physician Gerard van Swieten — also a pupil of Boerhaave — published a discourse on medicine in which he cried “may hypotheses be banned!”. And in the 1780s, when von Haller’s essay was being reprinted, the anthropologist Johann Karl Wezel proclaimed in broadly Newtonian spirit: “I only relate facts”.

Von Haller was aware of this anti-hypothetical fashion. He starts his essay by describing how naturalists had come to despise hypotheses. With the success of mathematical natural philosophy (the Newtonian form of experimental philosophy that had replaced Baconian natural histories), researchers started to rely (or at least, to claim that they were only relying) on what had been mathematically proven. This happened first in England with Newton, then in Holland with Boerhaave, then in Germany and France with Maupertuis and others.

For Haller, this was not a positive development. Peopled shifted from one excess, namely abusing of hypotheses, to an other, namely rejecting them altogether, while ignoring the virtuous middle way. Yet, while researchers were despising hypotheses, they were relying heavily on them:

    The great advantage of today’s higher mathematics, this dazzling art of measuring the unmeasurable, rests on a mere hypothesis. Newton, the destroyer of arbitrary opinions, was unable to avoid them completely. […] His universal matter, the medium of light, of sound, of the senses, of elasticity — was it not a hypothesis?

Von Haller makes other examples of natural-philosophical hypotheses, in order to highlight

    the true use of hypotheses. They are certainly not the truth, but they lead to it, and I say even more: humans have not found any way that is more successful in leading them to the truth [than hypotheses], and I cannot think of any inventor who did not make use of hypotheses.

What is this “true use of hypotheses”? It is their heuristic use. Hypotheses are claims to be tested by means of experiments and observations. Sets of hypotheses form large-scale systematic pictures that provide purpose and direction to our research. Think for instance of the heuristic value of the corpuscular hypothesis for the experimental activity of the early Royal Society (this is not von Haller’s example). Additionally, hypotheses make possible a public discussion of problems that scientists could not even mention if they were only allowed to talk about were facts, as some experimental philosophers hoped.

These experimental philosophers may reply to von Haller that they do not need to employ hypotheses to achieve those aims. All that is needed are queries. Von Haller would reply that queries are nothing else than hypotheses in disguise. “In fact, Hypotheses raise questions, whose answer we demand from experience, questions that we would not have raised if we did not formulate hypotheses”.

Von Haller was not the only author in the German-speaking world to provide a qualified defense of hypotheses. Christian Wolff before him and Immanuel Kant after him made similar points. However, von Haller was much more engaged in empirical research than either of them. His work seems to me to have been very much in the spirit of experimental philosophy. Finding such an explicit and detailed defense of hypotheses by such an author reminds us that the methodological views of early modern experimentalists were not monolithic and that, even in a strongly anti-hypothetical age, some authors were aware of the benefits of a careful use of hypotheses in the study of nature.

Experimental medicine and the Monro dynasty

Juan Gomez writes…

Following Peter Anstey’s post on 17th-century experimental medicine I want to continue shedding light on the topic, but I will be focusing on 18th-century experimental medicine. In particular, I want to examine the Monro dynasty and the role they played in the instruction of medicine in Edinburgh for more than a hundred years.

From 1726 until 1846 the chair of anatomy at the University of Edinburgh was held by the members of the Monro family. Alexander Monro Primus (1697-1767) held it from 1726 until 1754; his son Alexander Monro Secundus (1733-1817) succeeded him in 1758; and Alexander Monro Tertius (1773-1859) held the chair from 1817 until 1846. While Tertius’ relevance lies on the fact that he continued the work of his father and grandfather, Primus and Secundus are one of the main reasons why the medical school at Edinburgh was considered the best of its time. Of course, the experimental method applied by the Monro’s was one of the reasons for their success.

Monro Primus studied at Leiden under Herman Boerhaave in 1718, and by in 1720 he was back at Edinburgh giving public lectures on anatomy. In 1726 he published his Anatomy of the Humane Bones, which was widely read throughout the eighteenth century. The book was intended to be used by those students attending Monro’s lectures, where he demonstrated on corpses to illustrate the theory. In fact, the Professor’s insistence on the importance of performing dissections on corpses for his lectures was such that it was suspected that Monro and his students were grave robbing. In the preface to the second edition of his book Monro claims that all the facts included in his book, even those he has taken from other authors have been confirmed by experiments:

    In executing these [parts I and II of his book], I have taken all the assistance I could from Books, but have never asserted any anatomical Fact on their Authority without consulting the Life, from which all the Descriptions are made; and therefore the Quotations from such Books, serve only to do Justice to the Authors… Besides anatomists, I have also named several other Authors [for example Boyle] to confirm my reasoning by practical Cases.

Monro Primus was a very active figure in the Edinburgh enlightenment. As the editor of the volumes of essays published by his Medical Society of Edinburgh, he calls for the emphasis on facts and observation of the experimental method to be applied in Medicine. He tells us that he ‘principal part of medicine is:

    The Knowledge and Cure of Diseases, which chiefly depend on Observations of Facts that ought to be frequently repeated before any certain Axiom in Physick can be built on them.

Monro Primus’ work was continued by his son. Though Secundus continued using the text written by his father in his anatomy lectures, he published and contributed to the knowledge of the brain and the nervous system. All his texts contain detailed descriptions of the experiments he performed, besides the constant use of the rhetoric of the experimental philosophy and methodological statements confirming the use of experimental methods in medicine. A lot of his work stems from experiments performed on animals, notably a number of essays published in the collection of essays of the Royal Society of Edinburgh and his 1793 book Experiments on the nervous system, with opium and metalline substances, made chiefly with the view of determining the nature and effects of animal electricity. The way such book is structured is typical of experimental philosophy. Monro begins by giving some observations on the nervous system of frogs (which he used for his experiments); this is followed by a detailed description of the experiments and then he deduces “Corollaries from the above Facts and Experiments.”

In an earlier book, where he describes in some detail his main claim to fame (the discovery of the interventricular foramen of the brain), he calls for a stop to speculation and focus instead on facts and experiments. He refers to an experiment carried out by Dr. Albrecht von Haller which he describes and then tells us:

    But instead of speculating farther, let us learn the effects of experiments and endeavour from these to draw plain conclusions.

The contrast between speculative and experimental approaches is also stated in his last major work, Three Treatises. On the Brain, the Eye and the Ear (1797):

    An anatomist, reasoning a priore, would be apt to suppose, that the Water, in the Hydrocephalus Internus, should be as often found immediately within the Dura Matter, between it and the Outer-side of the Brain, Cerebellum, and Spinal Marrow, as within the Ventricles of the Brain. Experience, however, proves that it is generally collected within the ventricles; and, as I have not met with a single instance in which the Water was entirely on the Outer-side of the Brain, (although I am far from doubting the possibility of the fact), I cannot help suspecting that this happens much more rarely than it is supposed by Authors.

We can see then that the call for the application of the experimental method in medicine that started in the seventeenth century was characteristic of the medical school at Edinburgh in the eighteenth century. With the Monro dynasty in charge, the methodology promoted by Herman Boerhaave (Primus’ teacher) became the preferred for the training and practice of physicians in Scotland, with the Edinburgh medical school rising to its reputation of the best school in the world.