Criteria for Judging Theories

So how do we tell a good hypothesis or theory or model from a bad one? We test it. In fact, testability is one of the requirements of a scientific theory. If a hypothesis or theory fails a test, it is usually discarded or modified. I say "usually" because sometimes a theory is useful even though it is known to be faulty. For example, it might still explain more than any other theory, or it might be easier to remember. So what do we use to test a theory or model?

Essentially there are four criteria that we use to judge a theory or model. The first is that the theory must explain established observations. That is, it needs to be able to explain what is already known. Second, it needs to be able to explain new observations as they come up. If someone discovers something and that new discovery fits into the theory, then it is a good theory. On the other hand, if something is discovered that the theory cannot explain, then the theory is obviously wanting. The third thing is that the theory should be able to predict new observations. It should be able to tell you something new. You should be able to use the theory to say, "Now if this is true, then we should be able to find out something else "or" if this is true, then such and such should work; let's try it and see if it does." Fourth, in addition to all of that, it should be as simple as possible. Another way of saying that is that the theory should be simple if possible. Simple theories are preferred to more complex ones. If you can establish a theory that sets up four or five different rules or properties of materials that explain everything, that's much better than if you have to set up seven or eight or ten rules and then add a dozen different exceptions to those rules and so forth. So, if the theory is simple, that is a big plus.

Criteria for judging theories

1. Explain established observations.

2. Explain new observations.

3. Predict new observations.

4. Be simple.

So a good theory should be able to explain established observations, explain new observations, predict new observations, and do so as simply as possible. These criteria should be applied to any theory. Specifically, in this lesson, they will be applied to Dalton's Theory of Atoms.

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E-mail instructor: Eden Francis

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