Ask A Scientist© Biology Archive

Author:      scollins
Text:        I need good definitions for the following terms:  hypothesis, 
theory, law.  I teach high school biology and our textbook states that 
scientific laws - universal explanations of phenomena - do not exist in 
biology.  This leads to the inevitable student comment that everything I have 
taught them is "just a theory."

Response #:  1 of 1
Author:      moodywj
Text:        A hypothesis is a formal generalization, or tentative explanation 
for a set of data, or a group of observations.  A hypothesis allows scientists 
to design specific, do able experiments to test whether the tentative 
explanation will work on a new set of observations on the same subject.  A 
theory is a hypothesis that has been extensively tested to the point of being 
generally accepted as true.  Sometimes we use the term "law" for a very 
extensively tested theory, especially one that has an equation, or 
quantitative rule used to predict the outcome in a certain situation, e.g., 
the Law of Gravity.  It is a common error to assume that when a scientist uses 
the term "theory" that he or she means something which is still not yet 
believed or accepted.  This is not true.  The word is used for almost all 
principles because we do not really understand anything completely.  We speak 
of the theory of evolution, for example, even though virtually every reputable 
biologist in the world believes that evolution is a proven law.  However, some 
very important details are still being debated and tested, so the word theory 
is used.  Scientists are always testing.