2. The two parts of a scientific theory
The what and the why
This is the third post in this series. If you haven’t read the Introduction titled The Myth of Scientific Uncertainty, and post 1, you may want to do those first.
In the previous post, we saw that a scientific theory has two parts, the law or statement of relationship and the explanation for why nature acts this way. This is one of those concepts that is obvious, but not simple. The confusion comes from our tendency to merge these two aspects of knowledge in our minds. “This happens because…” When we use the word theory, such as Einstein’s Special Theory of Relativity, we mean both the hypotheses from which it was developed and the equations that he derived from them. They are as linked in our minds as the two sides of a coin.
Even though interdependent, a law and its explanation serve distinct purposes and have unique characteristics. Laws do the work. We use equations or logical statements to predict the outcomes of natural phenomena. Laws are generally quantitative. In science classes, we applied laws to solve the problem sets and tested their power of prediction in the lab. Then, on the job, scientists and engineers use them in the design of experiments and practical devices. The laws tell us ‘what’ but give us no information as to ‘why.’
Some laws are developed by adopting a premise and developing the consequences of that assumption. Einstein began by assuming the speed of light is the same regardless of the relative motion of the source and the observer. From this, he predicted the phenomenon of time dilation on moving objects. Such theoretically derived relationships can become laws when observations bear them out.
But more often, scientists form laws by developing an expression that generalizes a set of observations. Boyle measured the pressure of a constant amount of gas at different volumes and found that P times V is a constant. Early astronomers developed equations from which they could calculate the future positions of the planets. I have developed laws both ways, by solving the mathematical consequences of a hypothesis and finding it fit data in the literature[1] and by searching for a relationship that would meet my experimental goals[2],[3]. In either case, laws are confirmed by the consistent success of their predictions.
However, not having a plausible explanation for a phenomenon is problematic. We have a need to make sense of it. And this is not just true for scientists. As Hofstadter and Sandler say[4], “At every moment of our lives, our concepts are selectively triggered by analogies that our brain makes without let-up to make sense of the new and unknown in terms of the old and known.” In other words, we automatically seek an association between what we see and why it happens that way.
An observation is presumably something that actually happened; the associated explanation is our attempt to connect it with other things we ‘know’. It is the explanation that can change as we advance our study of the phenomenon.
Explanations, even though potentially tentative, play an essential role. As analogies or metaphors, they help us imagine or picture the phenomenon, they suggest other aspects of the phenomenon that we can then look for, and they add to the fabric of scientific knowledge through their links to other explanations. Their value is not in their truth but in their usefulness[5].
If we do not consider the law and its explanation separately, we can, and often have, declared the whole theory or concept invalid when it is just the explanation that has been disproved. The previously validated relationships continue to work as well as before.
In the next post, we will tackle the second pillar of science uncertainty, which is: consistency is no proof of certainty.
[1] Enke, C. G. Anal. Chem. 69, 4885-93 (1997).
[2] Christie G. Enke* and Gareth S Dobson, Anal. Chem. 79. 8650-8661 (2007).
[3] Christie G. Enke and Luc J. Nagels Anal. Chem. 83. 2539-2546 (2011).
[4] D. Hofstadter, Douglas, I. Sander, Surfaces and Essences, Analogy as the Fuel and Fire of Thinking (Basic Books, New York, 2013) p. 3
[5] Yucel, Robyn, Science & Education, 27, 407-413, 2018.
So clear. I'd like to think also about the ways that sometimes our explanations (the ones rooted in what is familiar or habitual) can make it difficult to observe what is happening, or contribute to ignoring information that doesn't fit what we expect.