when it is consistent with observation
If you're talking about what I think you're talking about, the fact that it is not "scientifically valid" might have a lot to do with it.
His theory of use and disuse was rejected.
Sorry but your question doesn't make sense... You have to know what the hypothesis is to test if your question is valid.
A scientific theory summarizes a hypothesis or group of hypotheses that have been supported with repeated testing. If enough evidence accumulates to support a hypothesis, it moves to the next step; known as a theory; in the scientific method and becomes accepted as a valid explanation of a phenomenon.
when it is consistent with observation
Guessing, inventing data.
You have to have a valid provisional licence and your provisional licence only becomes valid on your 17th birthday.
its to old
It is to old
Theory is a well-supported explanation or framework that can be used to understand and predict phenomena in a specific area of study.
Hypothesis
It is valid only for hydrogen like atoms.
A hypothesis, or group of hypotheses, that is accepted as consistently valid is a theory. Either a hypothesis or a theory can be ultimately disproven. One definition of a theory is an accepted hypothesis.
Based on his strong support for the war in Vietnam, he must have had at least some belief that the domino theory was valid.
It isn't.
Epistemological refers to the branch of philosophy that studies knowledge, how it is acquired, and what constitutes valid knowledge. It deals with questions about the nature, scope, and limits of knowledge and the justification of beliefs.