Theories, Laws, and Hypotheses

I was once walking with a group of friends, talking about random things, as they tend to go, when the subject of evolution was brought up. Obviously, this soon got into a huge argument from both sides, one side bringing up all sorts of evidences for the Theory of Evolution, while others contending that it's only a theory, and siding more on the side of creation. Hearing these arguments, it occurred to me that there were several uses of the word "theory" being put into play, and thus, decided I needed to work out exactly what a theory is.

Colloquially, the word theory seems to indicate at best a guess, perhaps educated. Many times I've overheard people saying things like:

"My car won't start. My theory is that the battery died."

"What's your theory on why they're late?"

"I'm sick. I think I have food poisoning." "That's only a theory."

However, in science, a word already exists that describes a sort of informed guess: a hypothesis. In fact, if we were to be precise on the matter, the previous statements would make more sense if they were:

"My car won't start. My hypothesis is that the battery died."

"What's your hypothesis on why they're late?"

"I'm sick. I think I have food poisoning." "That's only a hypothesis."

This being the case, what exactly is a "theory" then?

In middle and high school, I was taught the scientific method. I was told that when doing an experiment, first we need to have a hypothesis, which we then test via a controlled experiment, and get our results. Based on these results, our hypothesis can be promoted to a theory, which can then eventually be proven true to become a scientific law.

Balderdash.

Being in science for a few years, I've come to realize that not only is this view of the scientific method incorrect (to be discussed in a future post), but that these definition of theory and law are completely wrong and misleading. So what, then, is a theory?

Well... simply put, a theory is a framework of ideas based on a few assumptions that attempts to describe the natural world.

Notice that although assumptions are part of the definition (hypotheses!), a theory itself is not a guess of any sort. Rather, it takes those guesses and extrapolates them to try to understand more of the natural world. For example, take the Theory of Special Relativity. This theory is based off of two rather simple assumptions.

1. The laws of Physics are the same in all inertial (non-accelerating) frames of reference (the assumption of relativity).
2. The speed of light is constant in all inertial frames of reference (the assumption of the constancy of the speed of light).

From these assumptions, we get a mathematical framework describing space contraction, time dilation, and all sorts of other counterintuitive statements.

I should at this point mention that a theory does not, in fact, get "promoted" into a law when it get's "proven true". In fact, the philosopher Karl Popper argued that Theories of nature can never be, in fact, proven true, only falsified (in fact, he went on to say that if a framework cannot be falsified, it is not a theory). The reasoning behind this is simple: someone can always come up with a theory that describes nature the same way as a different theory. These two theories can lead to the same results, yet fundamentally, they are two different frameworks.

What then, you might ask, is a law, if not a theory proven true? Well, a Law of Nature is in fact just a generalization from observations of the behavior of a system. For example, Newton's Law of Gravity (which, by the way, is wrong in the sense that it has been disproved by the observations of the orbit of Mercury) states that the force of gravity between two objects is proportional to their masses and inversely proportional to the square of the distance between them. A law can be part of a larger theoretical framework, but it is in no sense, a theory which has been proven true.

Coming back to my friends arguing about the validity of evolution, we can see that at least part of the problem is the misinterpretation of the word "theory". Without a clear set of definitions, the meaning behind these words can be misinterpreted and twisted. Thus, although the phrase "It's only a theory, it hasn't been proven," implies that it may be shown to be false, this just means that it is, in fact, a good theory, one that can, in fact, be proven false. 

Due to the evidence for evolution, it is, at the very least, on the right track towards the true mechanisms. Whether that ultimately be due to some higher power or a purely naturalistic mechanism is, in fact, not even a component of evolution, or any natural theory. As a framework used to describe the natural world, a theory only has that ability, and nothing more.