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Monthly Archives: November 2011

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.