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.You might ask: will science collapse and be thrown into chaos by the “fine structure constant” variation finding, if true?
Michael Brooks, “Laws of Physics may change across the Universe,” New Scientist, 8 September 2010.
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.
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