Scientific Laws and Theories

To understand the difference between a scientific law and a scientific theory you need to have some understanding of the history of modern European science. It all kind of starts with the European Renaissance of the 14th through 17th centuries. As far as I can tell, it started in the arts and included people like Leonardo da Vinci and Dante. It got a boost and successfully spread because of the invention of movable type. Renaissance means rebirth. If we think of the period before the Renaissance as the Dark Ages, you can see why they called it a rebirth. Humanists of the Renaissance started studying the classic thinkers and started questioning "the way it has always been." The Renaissance, along with political changes, allowed the Protestant Reformation to gain a foothold. For our purposes, the main change, at least at first, was not a questioning of faith, but a questioning of the world view that had been passed down. That meant Aristotle. Aristotle was a great thinker and had developed many advances in physics and biology. His thinking was then adopted by the church and codified into church doctrine by Aquinas and others. Most of the great scientific thinkers of the time were Christians: Copernicus, Galileo, Newton, Descartes, etc. In fact, in his Meditations, Descartes offers a proof for the existence of God.

Two Books: Two Laws
Because these scientists where Christians they thought that the world was created by God. When they discovered how nature operated they thought that they were simply revealing the rules that God had set in place. The world was put together like a giant clockwork and it was the scientist's goal to figure out how this clock worked. Today the clock has been replaced by the computer as our inspiration, but back then it was the mechanical clock with all it's gears that dominated. The other dominant inspiration for Christians at that time was the Bible. The Bible was God's law. Since the 14th century theologians in the Catholic Church had been referring to the Book of Nature as God's other book. These two books were 'written' by God and represented two ways in which God's Law could be known. So it was natural, we might way, for Christians to see and label the things they were discovering through the scientific method as Laws. Newton's Law of Universal Gravitation is a good example. Newton did not create gravity, he simply discovered something that God had written into the way the world operated.

Laws do not exist unless there is a law giver. And since God had created the world and the rules that govern the world, it was natural to think of those regularities as laws of nature, because they were laws of the Supreme Law Giver. The two books theory of God's law had made its way into the language of the scientific revolution.

Two Things Happened
From this point on in the story two things happen which change the way the scientific community now thinks about nature. The first is that more and more scientists stop believing in God and so they no longer think of the regularities of nature as created by God. The idea of a law doesn't make as much sense without a law giver.

The second thing that happened is that some of these so-called laws were found to be wrong. Scientists became much more aware of the provisional nature of their discoveries. This brought about a more humble attitude in the scientific community. Even something as sure as Newton's Law of Universal Gravitation has been replaced with Einstein's Theory of Relativity.

Theory
Which brings us to the rise of scientific theory. In most academic disciplines, and even in less academic practices such as business management, there develops a specialized vocabulary. Terms that are used in everyday language are given special meanings that no longer communicate the same thing they do for the lay person. Philosophers are especially notorious for doing this. We call it jargon. So we have to be careful when we use specialized terms and take them out of context. For the lay person a theory is a guess. I have a theory about what my daughter has been doing when she stays out late at night. My theory is just a hunch or a guess. I don't have proof because if I had proof I would know and it would no longer be a theory. But scientists use the word hypothesis for guesses.

Once a hypothesis has been tested and analyzed by careful empirical observation and re-analyzed by other teams of researchers, then it becomes a theory. The word theory is reserved for those guesses that have come to be accepted among members of the scientific community who work in that specific area. Scientific consensus leads to the use of the term theory.

Science is very specialized. Physicists are not considered experts on theories of evolution. Geologists are not really qualified to make judgments about the latest stem cell research. So stem cell researchers compete with other stem cell researchers to see who will be the first to make some breakthrough and cure cancer or something. If you are first you could win the Nobel Prize, like Watson and Crick did for the structure of DNA.

There are Theories, and then there are Theories
Theories are not laws in waiting. Theories are at the top of the heap. Remember that Einstein's theory is better than Newton's law. That doesn't mean that all theories are equal. Experiments in physics can be conducted to very high degrees of specificity and confirmed with the same high degree of integrity. Physicists often have decisive refutations of hypotheses or experiments. But not all scientists have that same luxury. Theories about gene-environment interaction or studies involving human diet are a less likely to have definitive falsification.

Nevertheless, theories are the best we can do. Theories don't eventually get "proven" and become laws. Theories are already proven. Still, sometimes new ideas do get called laws. There are several reasons for this. Sometimes I think it's just a throwback to the earlier use of law by people who have not thought through the distinctions. Moore's Law might be an example of this. It's not really a natural law or theory about the world. So we still get things called laws, but they are not natural empirical regularities. Scientists are not philosophers, they don't worry about language as much. But there are specific examples that might go against my theory.

Statistical Laws
There are still a number of laws being put on the books. Gustafson's Law, Metcalfe's Law, Reed's Law, etc. But it seems to me that these are just various types of statistical laws based on sets rather than the kinds of theories generated by traditional scientific empirical observations.

In summary, my point is that without the idea of a law giver it does not make as much sense to label the regularities of nature "laws." And besides this, scientists have also adopted a more humble attitude toward their enterprise. A scientific theory is not some kind of inferior guess or some child that will some day grow up to become a law like a bill sitting on Capitol Hill.

Mind Over Body

Mr. Wright (not his real name, but that's what he's referred to in the literature), had cancer and was on the edge of death. His doctor figured he only had days to live. Mr. Wright was given a serum that he believed might cure his cancer. Sure enough, in just a matter of days his tumors disappeared. He was released from the hospital, happy and cured. A couple months later he read a report that the treatment he had received was no good. His tumors promptly grew back. Then his doctor convinced him that a new formulation of the serum was shown to be effective. He took it (this new formulation was just water) and once again he was cured. Another couple of months went by and he read more reports about that serum being a scam and completely useless. He died two days later. Thus is the power of our beliefs over our physical nature. We call this super power the Placebo Effect.

We all have this super power, which means medical research faces a particular challenge. Most scientific research subjects such as geology, astronomy, or paleontology do not have a vested interest in the research. A rock or a fossil does not care if you think it's a thousand years old or a billion years old. But a human has ideas about the research being done on him. And those ideas can change the very research being done.

If I give you a pill and tell you it will make the pain go away, there's a chance that your pain will go away even if the pill I gave you is nothing but a sugar pill. Presumably, sugar itself has no effect on your pain. So what's going on?

It's kind of like Neo in the Matrix: 

your mind makes it real. 

Here's a nice video explaining some
of the strange effects of placebos:

Because of the placebo effect, research on human subjects needs to control for it. What this means, in practical terms, is that people are divided up into groups. One group, for instance, will get the placebo and the other group will get the real medicine that is being tested. It's like a contest. If the medicine helps more people then the medicine wins, but if the percentage of people who took the placebo is about the same as the percentage of people who took the medicine, then that means that, as far as we can tell, the medicine actually didn't do any good.

No Better Than a Placebo

To be "no better than a placebo" is the ultimate failure for any kind of medicine, procedure, or other medical treatment.

Homoeopathy vs Placebo - as you might expect, the placebo wins.

Tylenol vs Placebo for Lower Back Pain - Placebos also win in contests where you might not expect them to win. For instance, acetaminophen can't beat a placebo for lower back pain.

You can do your own web search to find other placebo wins. It's not my goal to list them all. Whatever your favorite medical treatment for whatever ails you, it might not be a bad idea to search for placebo controlled studies to find out how effective it is.

Double-Blind

No, double-blind does not mean that the scientist conducting the study is blind in both eyes. It really means that neither the person taking the medicine/placebo nor the person dishing out the pills knows who is getting the placebo and who is getting the test drug. This is because we've found that if the doctor knows which pill they are giving to the patient they can give subtle hints that can adversely effect the study.

Even a horse is smart enough to read the subtle non-verbal cues. There's a famous case of the horse who could do math. His name was Clever Hans. People would give the horse simple math problems like 6-3 or 4+1 and the horse would tap it's foot up to the right number and then stop. What they found was that the owner of the horse would unknowingly give the horse a signal showing the horse that it was at the right number. When the owner was hidden behind a curtain the horse's math skills disappeared. Here's a picture of Clever Hans putting on one of his shows:

XKCD is right. Not every experiment can be double-blinded.

One of my favorite blogs, Science Based Medicine, has an article on Acupuncture that perfectly illustrates why blinding is important whenever it can be done. In this experiment someone who was not involved and had no knowledge about which children were getting the acupuncture should have done the evaluations. When the experimenter evaluates her own work she's not going to be the most objective observer. Blinding is necessary in order to counter confirmation bias, which we've discussed here.

So one of the important factors you need to consider when reading or hearing about some so-called scientific study is whether it was conducted properly. Doing good empirical studies on human beings is hard. So if it's possible, the study should include a placebo control group and, if possible, blinding both the patient and the doctor so that no one really knows who is in the study group and who is in the placebo group.

Actual medical research is more complicated that this. I would just like to take a second to point out a couple mitigating factors. For example, if there is a known effective (and by effective, I mean more effective than a placebo) treatment for some condition, then it would not be a good practice to withhold that treatment from people. So new medical treatments are sometimes put up against the known effective treatment in order to see if the new treatment is at least as effective, or more effective, than the known effective treatment. This means that not every piece of research will directly control for placebos. But if the known effective treatment was previously studied using a placebo control group then the new study can safely bypass a placebo control.

The other problem is that some things we want to know about are not testable in a laboratory very easily. Sometimes we want to know about lifelong habits and although this kind of study can be done on mice that only live two years, it's hard to do it on humans who are more likely to live seventy years. We'll deal with this problem in another post.

End Notes:
You can read more about Mr. Wright in The New York Times, Scientific American, or the original paper on Mr. Wright is here: Klopfer, Bruno, "Psychological Variables in Human Cancer", Journal of Projective Techniques, Vol.21, No.4, (December 1957), pp. 331–340.