Laws of Nature: modern science
The notion of laws of nature such as we use in today’s science began with the emergence of modern science in the seventeenth century. In its infancy it was linked to the notion that these laws were ordained by the Almighty Creator of the physical universe.
The first law of nature to be discovered in the modern use of the term was Kepler’s law of elliptic planetary orbits in the first decade of the 17th century. Kepler’s laws formulated universal aspects of a particular phenomenon (planetary motion). In the process they changed our study of celestial bodies, transforming astrology into astronomy.
Careful and systematic observations suggest that all natural phenomena arise from specific patterns of behavior of various parts of the physical world. In other words, the world, of which all that we experience are only small fragments, functions in methodical and systematic ways. Even when there seems to be apparent irregularity in behavior, one should be able to discover underlying regularities. Recognizable patterns in nature which have universal validity are referred to as physical laws or laws of nature. One is also able in most instances to uncover quantitative or mathematical dimensions to them.
The term law of nature arose from the notion that God imposed the observed or suspected regularities on nature. Leibniz emphasized the difference between truths of reason (necessary truths) and truths of facts (contingent truths), and said that the latter can be discovered only through observation and induction, and that, at the same time, they also have rational bases.
However, inasmuch as these laws are stated by humans on the basis of human observations – which are limited by several constraints – laws of nature are, in principle, subject to modification. From this point of view, there is nothing inexorable about them. All laws of nature are expressions in human language in terms of human concepts and terms. As E. W. Hobson pointed out, “a law of nature is in reality a conceptual law set up by the activity of the mind of man, but conditioned as regards its validity by the perceptual world which must be taken as a datum.”
There is no universally accepted view among philosophers on what a scientific law is. Philosophers of science have given a variety of definitions for this. Whatever definition one adopts, at any given point of time it would be difficult, if not impossible, to assert whether a given statement, in spite of all its concordance with observed facts, is in fact a law or not. Take, for example, the relationship between the pressure and the volume of a given amount of gas at a specified temperature. This relationship, generally known as Boyle’s law, was taken to be true until more careful observations at high pressures revealed discrepancies between the law as stated and results of observations. Later it was found that the law is only an approximate description of how gases behave, and was accordingly improved upon. Similarly, the so-called law of Delong and Petit of specific heats of solids was accepted as true for many decades until precise experiments at very low temperatures proved it to be invalid there. Many such instances may be found in the history of science. One way out of the difficulty is to state right away that any experimentally deduced law holds only within a well-specified range of observations. In case of laws which are not derived directly from experiments, this will not be possible.
The potential mutability of physical laws has prompted some anti-science philosophers to argue that scientific knowledge is untrustworthy. Some philosophers of science have declared that the laws of nature as formulated by science are mere conventions. However, it is important not to trivialize something whose role and significance are far greater than conventions. Such criticisms generally come from those who have not practiced science themselves or from thinkers who recognize the limits of human knowledge at a profounder level. Most scientists are quite aware of the tentative nature of scientific knowledge. They don’t regard it as science’s weakness, but rather as its strength. Uncertain truths, fortified by experimental verification, are often more reliable than dogmatically held claims which have no criteria for universal acceptance.
In view of this, one may adopt the following definition: A law of nature is a suspicion of a particular pattern of behavior of a certain aspect of nature in a specific frame of reference. By frame of reference, we mean the conditions under which the law is applicable. The frame of reference for Boyle’s law is gas under low pressure. The frame of reference for Newton’s law of notion is velocities small compared to the speed of light.
We are talking about a pattern of behavior and not behavior as such. What this means is that a law of nature is a general statement, not particular. The statement that Mars moves in an elliptical orbit is not a law. But the statement that all planetary bodies move in elliptical orbits around their central star is a law. The statement that copper expands on heating is not a law, but that all metals expand on heating is a law. As long as there is no reason to believe that the suspicion about a general pattern of behavior of some aspect of the physical world is not shown to be mistaken, it is taken as a law of nature, i.e. as reflecting an intrinsic feature of the world. With this understanding, a law may be exploited for theoretical consistency as well as for practical purposes.
This definition raises an important question: Is scientific knowledge, much of which is condensed in the statements of the various laws of nature, merely a subjective matter, as seems to be suggested in this definition? For the word suspicion implies what we think, rather than what is out there. Science seems to lose its great virtue of objectivity in this view. In answer to this, we simply note an important lesson that is forced on us from the history of science is that no law of nature, as stated by humans, can be regarded as the final unalterable truth. As illustrated above, many laws, once categorized as being inexorably true, have been found to be either only approximations or even totally wrong in the long run. It is therefore wise to be cautious in our assertions. Also, a suspicion of a state of affairs does not necessarily deprive that state of all objective existence. It is quite possible that the suspicion is correct.