What are those things we call “laws of nature”?

There was a recent post at Aeon by philosopher Marc Lang:

• What is a law of nature?

I want to discuss that, and to discuss some of my disagreements. My first disagreement, is that I don’t believe there are such things as laws of nature. But there are certainly things that people call “laws of nature”. I’m okay with calling them scientific laws. But I doubt that they come from nature. That is to say, I see these laws as human constructs. I do not see them as something that we can just read from nature itself.

In our science classes, we all learned some examples of what scientists currently believe (or once believed) to be laws of nature. Some of these putative laws are named after famous scientists (such as Robert Boyle and Isaac Newton). Some are generally called ‘laws’ (such as the laws of motion and gravity), while others are typically called ‘principles’ (such as Archimedes’ principle and Bernoulli’s principle), ‘rules’ (such as Born’s rule and Hund’s rule), ‘axioms’ (such as the axioms of quantum mechanics), or ‘equations’ (such as Maxwell’s equations).

It is interesting to note the expression “what scientists currently believe (or once believed) to be laws of nature” for that already suggests that scientists can change their minds as to what they take to be laws of nature. And this seems to agree with my point that these laws are actually human constructs.

The author, Lang, is clearly aware that scientists can change their minds. For he clarifies what he is discussing, with:

“By ‘laws of nature’, I will mean the genuine laws of nature that science aims to discover, not whatever scientists currently believe to be laws of nature.”

My own skeptical view is that there are no genuine laws of nature. And if there are no genuine laws to discover, then scientists cannot be discovering them. At best, they can only construct what they take to be laws.

Necessity

Lang asks about laws, “Just what kind of necessity do they possess?” He sees this as an important characteristic of such laws:

What all of the various laws have in common, despite their diversity, is that it is necessary that everything obey them. It is impossible for them to be broken. An object must obey the laws of nature.

This does not work for Boyle’s law. According to Boyle’s law, the pressure and volume of a body of gas are related by  where is just a constant. This assumes that everything else (particularly the temperature) does not change. This is an important law of physics. Yet it is does not have the kind of necessity that Lang wants. I learned about Boyle’s law in high school, and it was immediately obvious that it can be broken. It was obvious, because I already knew that if you compressed a gas enough, it would liquefy. And Boyle’s law would not allow that to happen. So Boyle’s law must fail as the gas approaches the point of liquefication. This was obvious to me as a high school student, and it is surely obvious to all physicists. So Boyle’s law fails the requirement that it cannot be broken. Perhaps Lang can simply say that it is not a genuine law. The physicists deal with this by describing as an ideal gas law. That is, it is true for imagined ideal gasses, but it is not quite right for actual gasses.

We can look at Newton’s laws as another example. These days, most physicists will say that Newton’s laws are false. But there was a time in the past when Newton’s laws were considered to be necessary. So we can examine what kind of necessity they had at that time. As I see it, Newton’s laws were necessary because they were analytic statements. That is to say, that were true by virtue of the meanings of their terms. But today, Newton’s laws are seen as false, mostly because of other developements in science such as Einstein’s relativity.

How is that possible if Newton’s laws were analytic? Quite simple, the meanings of the terms have now changed in subtle ways, so that Newton’s laws are no longer analytic in terms of the current meanings.

Rules of the the game

Lang looks at the rules of chess, to consider a particular kind of necessity. But he does not see that as applying to laws of science:

The natural laws obviously do not ‘govern’ the Universe in the way that the rules of chess govern a game of chess. Chess players know the rules and so deliberately conform to them, whereas inanimate objects do not know the laws of nature and have no intentions.

He is right that inanimate objects have no intentions and do not follow laws as rules. He is looking at scientific laws the same way as most people do. And that inanimate objects are not obliged to follow our laws seems to make laws mysterious.

I look at this rather differently. I see the laws of physics as the rules of the game of physics. The physicists do know these rules, and they do deliberately conform to them.

That standard view of Newton’s second law, is that when a force is applied to an object, then that object will accelerate in accordance with . Looked at from my perspective, however, Newton’s second law is telling the physicist that when he sees an object accelerating, he must ascribe a force as the cause of that acceleration. So I see it as a rule for physicists to follow, rather than a rule for inanimate objects to follow. In effect, I see Newton’s laws as rules for physicists to follow when using terms such as mass, velocity, acceleration, force. If we go with Wittgenstein’s saying, that meaning is use, then by defining the rules on how we use those terms, Newton’s laws are implicitly establishing the meanings of those terms. And that’s why Newton’s laws were analytic. But these days, physicists instead use rules from Einstein’s relativity, which are subtly different and lead to subtly different meanings.

Pragmatism

A mistake that is often made, is to assume that scientific laws are valued because they are true. In practice, however, they are valued because they are very useful. That’s a pragmatic judgement rather than a judgement of truth. Boyle’s law is a good example of this. As discussed above, it is not strictly true. But it still works very well for the situations where it is used. Likewise, Newton’s laws are often seen as false, in the light of relativity. Nevertheless, Newton’s laws work well for many uses, and they are easier to use than the corresponding statements from relativity.

Can laws be analytic?

A view I often see expressed, is that analytic statements are tautologies and therefore have no actual value. So they could not be scientific laws. I disagree with that, and I did discuss that in an earlier post.A

As I see it, the mistake is to view laws as propositions. When considering a statement to be a proposition, you are presupposing the meanings used and folding those in as part of the proposition. That cannot work when part of the role of the law is to implicitly define the meanings being used.

Scientific laws are not all analytic. As discussed above, Boyle’s law is false, so cannot be an analytic truth. However, because the laws are very useful, they are much used. And if we go with Wittgenstein’s “meaning is use”, then those laws will tend to affect meanings. It should not be a surprise if, as a result of using these laws, the scientist’s meanings shift toward making the laws analytic.