“How  much confidence do scientific theories deserve?”

Leon Brillouin:

 At this point we may raise a most important question: How  much confidence do scientific theories deserve? The answer must be  cautious enough: a good deal, but not too much! There are  limitations to all our theories; they are good up to a certain limit  and within certain boundaries. They do not represent ” The  truth, nothing but the truth….” Every theory is based on  experiments that have been checked very carefully, but the result can only be stated ” within possible errors ” between fixed  limits according to the best knowledge of the experimenter. There  is always a possibility that a new, unpredictable cause of errors  might be playing a role in a new experiment, or that the theory  has been extrapolated too far from its domain. 

– Relativity Re-examined