To the sort of person who demands evidence...?

Evidence, evidence, evidence. Scientists don't "give the evidence," they interpret it. Similarly, forensic detectives interpret the evidence at a crime scene, and DAs deliver those interpretations to the jury. Scientists do use basic assumptions to interpret those pieces of evidence. The first assumption they make is that they can trust their eyes, ears, &c. to be trustworthy. Why is it so difficult to admit that?