Where Clifford’s rule is right to follow:

"Whenever the option between losing truth and gaining it is not momentous, we can throw the chance of gaining truth away, and at any rate save ourselves from any chance of believing falsehood, by not making up our minds at all till objective evidence has come." (P 101f)

Where Clifford’s rule is not right to follow:

" . . . where faith in a fact can help create the fact, that would be an insane logic which should say that faith running ahead of scientific evidence is the lowest kind of immorality" into which a thinking being can fall." (P 103a)