There cannot be two sets of truth when one does not agree with the other. One or the other is true, but not both. Sincerely believing something, and practicing that belief, will not make it right if it really is wrong. How should you feel if proof is given that what you believe is wrong For example, say that you were in a car, traveling for the first time to a certain place.

Short article on GRASS from U.S. Army Construction Engineering Research Laboratories (CERL), the developers.