There are many words which take a very different meaning in their scientific context to what they might mean in everyday use.
When people talk about having a theory in everyday language, usually they mean a hypothesis with very little evidence to back it up. A hunch, a feeling, a guess, an idea.
In science, a theory actually falls at entirely the other end of the spectrum. A theory is an explanation of the mechanism of how an observed phenomenon comes about which is strongly supported by empirical evidence.
A theory is different from a law not in the strength of it’s evidence, but in what it tells you. A theory deals with the mechanism behind a phenomenon. A law describes a phenomenon without dealing with how it comes about. If you like, a theory is an explanation, a law is a description.
This distinction causes a lot of confusion when it comes to the theory of evolution by natural selection. Evolution as a process is an observed phenomenon, not a theory. It can be seen in the lab. It can be exploited through deliberate selection by humans to create and modify domestic animal breeds. The theory part — the part that describes the mechanism — is “by natural selection.” To talk about the “theory of evolution” is to use a shorthand for the actual theory, compounding the confusion caused by not knowing the different scientific meaning of the word “theory”.
- Don’t fear the facts. Learn about the Theory. (thinkingscifi.wordpress.com)