Did Hume deny the Physical Necessity of Laws of Nature?

For a long time, Hume was thought to have denied that causation or laws of nature have a physical or natural necessity, and he was held to have been an advocate of the “regularity” theory of natural laws, which shuns the necessitarian view.

Bertrand Russell, for example, held this reading of Hume, and passed it on to the logical positivists, as A. J. Ayer explains in the video clip below.



However, recent Hume scholars have disputed this view:

“More recent scholarship refutes this earlier ‘standard’ reconstruction of Hume. … What Hume denied was that there was any empirical evidence for necessity. His so-called skepticism concerned our finding out that physical laws are nomological. But his skepticism about our ability to find evidence did not carry over to a skepticism about the existence of such necessity. He had a belief in such necessity; his problem was to justify that belief rationally and he found it difficult to do so.” (Swartz 1995: 82).

Amongst these recent scholars are Wright (1983) and Strawson (1989). There is also a good summary of the new reading of Hume here.

Whether Hume really ascribed to this view or not, it does have a certain merit in carefully distinguishing the (1) ontological from (2) epistemological necessity of laws of nature.

We cannot prove by deductive argument that the laws of nature have a physical necessity. We can, however, propose inductive arguments and use inference to the best explanation to infer that it is probable that certain fundamental regularities as described in physics have a physical/natural necessity in our universe.

But the epistemological issue is that inductive argument does not yield certainty, and, paradoxically, the idea that laws of nature have physical necessity remains an empirical hypothesis/theory that is fallible in that it could be wrong, though we would need empirical evidence to prove this too.

BIBLIOGRAPHY
Strawson, Galen. 1989. The Secret Connexion: Causation, Realism, and David Hume. Clarendon Press, Oxford.

Swartz, Norman. 1995. “The Neo-Humean Perspective: Laws as Regularities,” in Friedel Weinert (ed.), Laws of Nature: Essays on the Philosophical, Scientific and Historical Dimensions. Walter De Gruyter, Berlin. 67–91.

Wright, John P. 1983. The Sceptical Realism of David Hume.Manchester University Press, Manchester.

Types of Necessity and Laws of Nature

Do laws of nature have necessity? And if so, then what type of necessity do they have? These questions are not just of interest to philosophers of science, but also are relevant to alleged “laws” of economics.

The trouble is that philosophers these days tend to recognise more than one form of necessity, as follows:

(1) Logical necessity
Logical necessity is a property of a proposition, and means that the idea expressed by the proposition could not have been false: its negation is a self-contradiction.

Logical necessity is found in (1) analytic a priori propositions where it is grounded in consistent use of language or (2) the conclusion of valid and sound deductive argument (the only possible though still debatable exception is a highly qualified version of Descartes’ cogito argument).

In this sense, logical necessity is an epistemological/epistemic concept and a property attached to propositions. It can be called de dicto necessity.

In short, as an epistemological concept, we can know with apodictic truth that a proper analytic a priori proposition is necessarily true.

The opposite of logical necessity is contingency: a contingent proposition is one whose negation is possible, and not a self-contradiction. Again, the concept is epistemological/epistemic.

(2) Metaphysical necessity
There is a second type of necessity that is ontological, not epistemological/epistemic.

For something to have metaphysical necessity is for it to be necessarily true in all possible worlds: a necessity that obtains in all logically possible worlds. This is a type of modal de re necessity.

(3) Physical/natural necessity
Again, this is a type of necessity that is ontological, not epistemological/epistemic.

The necessity is grounded it what is assumed to exist in nature. A physical/natural necessity is one that is ontologically necessary in our universe or any possible universe with the same laws of nature (considered with respect to that particular universe).

In addition, nomic necessity or nomological necessity is a type of ontological necessity that is a property of things guaranteed by laws of nature in our universe.

The Humean and logical positivist view is that all necessity is de dicto necessity, but modern analytic philosophers following the metaphysical revolution of Kripke deny this.

The laws of nature are clearly not logically necessary because they are not analytic (that is, true by virtue of definition of terms) nor are they formally logically necessary (Ellis 2002: 109).

But some modern philosophers, adopting an epistemological category taken from Saul Kripke, think that the laws of nature are necessary a posteriori, in the sense that even though they are known empirically (or a posteriori) they are ontologically or physically necessary in our universe (Ellis 2002: 109).

There is also a sense – and this is where it gets complicated! – in which the specific laws of nature in our universe could be metaphysically contingent (in that they could be different in other possible universes) but at the same time physically necessary when considered with respect to things within our universe: they have metaphysical contingency but physical necessity.

But the necessity here is not epistemic, but ontological or de re necessity.

So Hume’s problem of induction and the problems with necessary laws of nature can be recast or indeed properly interpreted as a fundamental epistemological issue: can we know that laws of nature are physically necessary in our universe? All the arguments adduced for the ontologically necessary a posteriori status of laws of nature are still based on empirical evidence and inductive argument, and so are fallible given that induction does not yield certainty. It may be that laws of nature are physically necessary, but, epistemologically speaking, we cannot be certain that they are.

Paradoxically, the proposition “that laws of nature are physically necessary in our universe” remains a synthetic a posteriori statement whose truth is highly probable at best, because the concept of necessity used here is ontological, not epistemic.

Links
“David Hume,” Stanford Encyclopedia of Philosophy, 2001 [rev. 2009]
http://plato.stanford.edu/entries/hume/

Fieser, James. “David Hume (1711–1776),” Internet Encyclopedia of Philosophy
http://www.iep.utm.edu/hume/

“Laws of Nature,” Stanford Encyclopedia of Philosophy, 2003 [rev. 2010].
http://plato.stanford.edu/entries/laws-of-nature/

Swartz, Norman. “Laws of Nature,” Internet Encyclopedia of Philosophy
http://www.iep.utm.edu/lawofnat/

BIBLIOGRAPHY
Ellis, Brian David. 2002. The Philosophy of Nature: A Guide to the New Essentialism. Acumen, Chesham.

Laws of Nature: The Historical Background

Many economists think that their disciple discovers “laws,” and the belief in “laws of economics” stems from the idea of laws of nature in the natural sciences. The tendency is seen in both neoclassical and Austrian economics and Marxism.

But what is the background to the concept of “laws of nature” in physics and the natural sciences? What is the epistemological status of a proposition expressing a “law of nature”? How do “economic laws” compare with laws of nature?

This is a very complex issue, but the crucial point is this: there are reasonable – and certainly well known – traditions in modern science and philosophy of science that allow us to dispense with the very idea of a universal, necessarily true law of nature. But why does economics maintain the idea of universal economic laws? The answer is simply that economists and economic methodologists have failed to notice that they are using an old and (arguably) discredited philosophy of science.

In this post, I merely want to examine the background to the idea of physical “laws of nature.”

A “law of nature” has been defined as a fundamental regularity observed in nature or of natural phenomena that holds for all places and all times. In this sense, a “law of nature” can be defined as a true empirical statement of universal form that is necessarily true, not contingently true.

The earliest of the early modern philosophers/scientists who developed the notion of “laws of nature” and was influential in causing others to use the idea was Descartes: he combined the theological notion of god having “legislated” laws for nature with the view that these regularities are predictable by means of quantitative rules and mathematics, though scholars claim that earlier writers anticipated this usage (Ruby 1986: 342–344), and the idea of “laws of nature” in a general sense can be found even in the writings of some ancient Greek and Roman thinkers (Zilsel 1942: 260; Lehoux 2012: 55; Milton 1981: 174).

Descartes argued that the universe as created by god had an orderly and knowable nature described in terms of mathematics.

The rise of this view was part of the collapse of the prior Aristotelian Weltanschauung in which the universe was seen as organic, geocentric, and characterised by formal and final causes, and teleology.

Why the new worldview that displaced the Aristotelian one arose at this time is debated. Zilsel (1941; 1942) attempted a sociological Marxist explanation, and argued that the idea of natural law as determined by god arose from the rising environment of political absolutism in Europe and the emergence of experimenting capitalist artisans searching for quantitative rules of engineering and design. These explanations are not very convincing, given that the two necessary conditions have been present in many civilisations but these societies never developed the concept of “laws of nature” as defined above (Milton 1981: 178–181).

On the contrary, it seems that philosophers and thinkers in general were already moving toward the idea of “laws of nature” in the early modern period, and that discoveries in the sciences and theology assisted the development of the idea.

In particular, both the divine command theory of ethics and the natural law theory of ethics probably influenced the emergence of the doctrine of “laws of nature”:

“When Descartes spoke of God’s having imposed laws upon nature, all he really had to do, therefore, was to transfer from the moral order into the realm of natural philosophy the well-established theological doctrine of an omnipotent Legislator-God, whose sovereign will lies at the very heart, not only of the divine laws revealed in the Scriptures, but also of that natural law to which right reason is man’s unswerving guide. There can be little doubt that he was familiar with this tradition … .” (Oakley 1961: 441).

So too William of Ockham’s philosophy may have played a part (Oakley 1961: 443). And, above all, the new discoveries that were made in this era gave the fundamental impetus to the emergence of the belief in underlying “laws of nature.”

So the “laws of nature” in the classical scientific sense stemming from the early modern period and the work of Descartes and Newton are laws created by god to govern the behaviour of the universe (Giere 1995: 123), although many also believed that god could suspend these laws to effect miracles and that he could also have created a universe with different laws.

In general, the “theological” interpretation of laws of nature was very influential and was probably the dominant view until the 19th century, although by the 18th century deist and rationalist thinkers no longer thought that god caused any supernatural miracles in our universe, and that the universe was strictly governed by natural laws.

Gradually, a “secularisation” of scientific thought occurred with the triumph of the theory of Darwinian evolution, and there arose the view that laws of nature did not necessarily require god or any supernatural creator being (Giere 1995: 127).

Giere sums up the state of affairs in the 20th century:

“It is the secularized version of Newton’s interpretation of science that has dominated philosophical understanding of science in the twentieth century. Mill and Russell, and later the Logical Empiricists, employed a conception of scientific laws that was totally divorced from its origins in the theological climate of the seventeenth century. The main issue for most of this century and the last has been what to make of the supposed ‘necessity’ of laws. Is it merely an artifact of our psychological make-up, as Hume argued, an objective feature of all rational thought, as Kant argued, or embedded in reality itself?” (Giere 1995: 127).

In the 20th century, the very notion that laws of nature must have universal, physical or metaphysical necessity came under attack.

There was also an epistemological question too: how can we really know that a law of nature is necessarily true and valid in places and all times?

Although I certainly do not deny that there are still influential and prominent scientists and philosophers of science who regard laws of nature as necessary a posteriori truths (a view related to the return of metaphysics into later 20th century analytic philosophy), nevertheless the whole topic is open to debate, and old ideas are very much in doubt.

I provide only the briefest of sketches of this debate below.

The logical positivists were influential in questioning the traditional idea of a necessary natural law.

Ayer (1956: 145) pointed out that many think that the laws of nature have a kind of necessity attached to them, though this is difficult to define and defend. The view that laws of nature are inviolable laws established by god requires good reasons to believe in such a god, and it cannot be sustained if there are no good arguments for god’s existence.

Taking up David Hume’s notion of constant conjunction, the logical positivists argued that laws of nature are just empirical regularities to which we have found no exception, and need not have logical nor physical/metaphysical necessity.

Giere (1995: 130–130) proposed that many scientific laws such as Newton’s laws of notion can be given an abstract status.

Newton’s strict laws of notion, for example, can be construed as abstract laws, and be used to construct scientific models, in the same way mathematicians construct analytic a priori systems in pure mathematics. These models have necessary truth, but that logical necessity is a product of their non-empirical, analytic a priori character.

But, when we apply a model to reality or to some specific natural system or phenomenon, its usefulness consists in how well it “fits with” and describes reality, and even though the “fit” may not be perfect, the models do capture real ontological structures of nature (Giere 1995: 131). This “constructive realism,” which is a realist reformulation of van Fraassen’s instrumentalist view of science, does not, however, require strict, universal laws of nature at all.

In a moderate empiricist view of science, one could also argue that abstract laws and models get an empirical hearing when applied to the real world, so that any law asserted of the real world can only be true contingently and known as true a posteriori.

There might be physical reasons why laws of nature really are physically necessary in our universe, but the hypothesis that they are physically necessary cannot be known a priori and must remain an empirical proposition. That is, there are profound epistemological problems that prevent us from knowing whether laws of nature really are eternal, universal, and necessary.

In addition, the Popperian view of science as the process of creating falsifiable hypotheses and continuously subjecting these hypotheses to further testing and rejecting those that are falsified seems to not even require that science discovers irrefutable, necessarily true knowledge of the universe.

To conclude, one might note that a few years ago some remarkable evidence was reported that the “fine structure constant” (or what is called “alpha”) – a fundamental law of nature – may not be constant throughout the universe:

“Laws of Physics Vary Throughout the Universe, New Study Suggests,” Sciencedaily.com, 9 September, 2010.

Michael Brooks, “Laws of Physics may change across the Universe,” New Scientist, 8 September 2010.

You might ask: will science collapse and be thrown into chaos by the “fine structure constant” variation finding, if true?

Not at all. This is because many working scientists and philosophers of science have long since moved on from the view that science discovers immutable, eternal, and necessarily true laws of nature.

BIBLIOGRAPHY
Ayer, A. J. 1956. “What is a Law of Nature?,” Revue Internationale de Philosophie 36: 144–165.

Giere, R. 1995. “The Skeptical Perspective: Science without Laws of Nature,” in F. Weinert (ed.), Laws of Nature. de Gruyter, Berlin. 120–138.

Giere, Ronald Nelson. 1999. Science without Laws. University of Chicago Press, Chicago, Ill. and London.

Gribbin, John R. 2003. Science: A History 1543–2001. Penguin, London.

Harrison, Peter. 1995. “Newtonian Science, Miracles, and the Laws of Nature,” Journal of the History of Ideas 56.4: 531–553.

Henry, John. 2004. “Metaphysics and the Origins of Modern Science: Descartes and the Importance of Laws of Nature,” Early Science and Medicine 9.2: 73–114.

Inwood, Brad. 2005. Reading Seneca: Stoic philosophy at Rome. Clarendon Press, Oxford.

Lange, Marc. 2008. “Laws of Nature,” in Stathis Psillos and Martin Curd (eds.), The Routledge Companion to Philosophy of Science. Routledge, London. 203–212.

Lehoux, Daryn. 2012. What did the Romans Know?: An Inquiry into Science and Worldmaking. University of Chicago Press, Chicago and London.

Martin, Michael. 1990. Atheism: A Philosophical Justification. Temple University Press, Philadelphia.

Milton, John R. 1981. “The Origin and Development of the Concept of the ‘Laws of Nature,’” European Journal of Sociology / Archives Européennes de Sociologie 22.2: 173–195.

Needham, Joseph. 1951a. “Human Laws and Laws of Nature in China and the West (I),” Journal of the History of Ideas 12.1: 3–30.

Needham, Joseph. 1951b. “Human Laws and Laws of Nature in China and the West (II): Chinese Civilization and the Laws of Nature,” Journal of the History of Ideas 12.2: 194–230.

Oakley, Francis. 1961. “Christian Theology and the Newtonian Science: The Rise of the Concept of the Laws of Nature,” Church History 30.4: 433–457.

Psillos, Stathis. 2007. “Laws of Nature,” in Philosophy of Science A–Z. Edinburgh University Press, Edinburgh. 135–140.

Rosenberg, Alexander. 2012. Philosophy of Science (3rd edn.). Routledge, New York.

Ruby, Jane E. 1986. “The Origins of Scientific ‘Law,’” Journal of the History of Ideas 47.3: 341–359.

Van Fraassen, Bas C. 1989. Laws and Symmetry. Clarendon Press, Oxford.

Zilsel, Edgar. 1941. “Physics and the Problem of Historico-Sociological Laws,” Philosophy of Science 8.4: 567–579.

Zilsel, Edgar. 1942. “The Genesis of the Concept of Physical Law,” The Philosophical Review 51.3: 245–279.

Zilsel, Edgar. 2000. “The Genesis of the Concept of Physical Law,” in Diederick Raven, Wolfgang Krohn, and Robert S. Cohen (eds.), The Social Origins of Modern Science. Kluwer Academic Publishers, Dordrecht and London. 96–122.