Characteristics of a "good" theory
1. A theory is better if it accurately reflects the facts of the real world.
2. A theory is better if it is stated in a way that makes it clearly understandable to anyone who is reasonably competent.
3. A theory is better if it not only explains the past, but helps predict the future with specifics.
4. A theory is better if it offers practical guidance in solving daily problems.
5. A theory is better if it is internally consistent (should fit together logically).
6. A theory is better if it is economical in the sense there are as few unproven assumptions as possible and it explains as much as possible (law of parsimony).
7. A theory is better if it is falsifiable or disconfirmable.
8. A theory is better if it stimulates new knowledge.

9. A good theory is one that makes good sense.

Adapted from Comparing Theories of Child Development (4th edition), by R. Thomas