30 March 2007

How Science Works: Hypotheses, Theories, and Laws

As you all may or may not recall, I argued last week that observation alone does not constitute science, and that discerning patterns in the natural world is essential to both formulating and testing a hypothesis. It's a point that I would hope be obvious to anyone with any kind of education in science, but I was shocked to learn how vehemently some of the students in my ecology class disagreed with it. Today I want to touch on another controversy that arose from that class: the difference (if any) between theories and laws.
First, I ought to define my terms. When I use the word 'theory,' I am using it in the true sense of the word; that is to say, I am not using it synonymously with 'hypothesis.' A hypothesis is effectively a guess (ideally an educated guess, as per Part One of this post) that has yet to be proved. A theory is a scientific fact; in a sense, it is a hypothesis that has been tested enough times and with sufficient rigor to have been proved beyond a reasonable doubt. Again, I would hope that this would be common knowledge, but the two words have become increasingly conflated (thanks in part to the active efforts of the Discovery Institute and other supporters of "intelligent" design) to the point where most scientists I know use the phrases "in theory" and "hypothetically" interchangeably. However, this point has been made several times by people far more eloquent than me, so I won't belabor it any further here.
The real purpose of this post is to address what I consider to be a particularly irritating conceit of the physical sciences. It often seems to be assumed that the fundamental theories of physics and chemistry are somehow more valid than those of natural sciences, such as evolution or plate tectonics, and as such are often considered to be laws rather than "just" theories. However, this gulf between "hard" and "soft" sciences is merely one of degree, and does not reflect any fundamental differences. I won't for a moment deny that physical theories have much more predictive power than biological or geological ones, but this is in part because biologists and geologists deal with staggeringly complex systems, whereas physicists and chemists often consider the processes they study to be occurring in a vacuum. Of course, this is not generally the case, and as such even predictions made based on physical "laws" are often inaccurate (Think, for example, about when you took classes in chemistry: were you ever able to exactly predict the relative proportions of the products of a reaction?). My point here is more philosophical and semantic than scientific: the word 'law' implies an immutability that does not exist in science. If you were able to say beyond a shadow of a doubt that a formula could predict the outcome of a process 100% of the time, then it would be perfectly appropriate to consider that formula a law. However, how can you prove such unerringly accuracy? Even if every experiment you perform confirms the precise predictive power of your formula (which in itself would be unlikely), to assert that this predictive power was universal would, by definition, require a knowledge of the entire universe. What's more, it would require knowledge of the universe not just as it is now, but as it has been and will be. Clearly, no human has ever possessed such knowledge. As such, claiming that any scientific "law" is universally applicable is a leap of faith, and blind faith is the antithesis of science. Rather, a "law" is nothing more than a theory: a hypothesis proved beyond a reasonable doubt, but that cannot be applied universally within the framework of science. This fundamental indecisiveness may seem to cheapen science, but it in fact reflects its greatest strength: accepting nothing as dogma and always leaving room for skepticism.
Once again, I've probably well overstepped the bounds of my own knowledge in writing this post; after all, I'm only a simple paleontologist. As with my last post of this nature, I'd be very curious to know what you all think; I realize I might just be ranting here, and I'd be really curious to know where other people stand.

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