American Scientist

To the Editors:

Greg Ross says in his article entitled "Descending Scales" (Science Observer, May–June), "Biologists agree that [snakes] descended from lizards, but exactly where this first happened has been a matter of debate since the 1800s, when two contending theories emerged." Ross then goes on to explain two contending hypotheses which he, very rightly, calls "hypotheses," not "theories."

Scientists and science writers have a disturbing tendency to misuse these two words. In the vernacular, "hypothesis" and "theory" can be used interchangeably. However, in the scientific literature, scientists and science writers must be careful to distinguish between these two terms. A hypothesis is a tentative explanation that can be tested through investigation; a theory is an established set of ideas that can be used to make predictions.

Scientists and science writers themselves must make a conscious and concise distinction between the use of these terms if they expect the general public to make such a distinction.

Paula E. Cushing
Denver Museum of Nature & Science