  while I do not, simply because you know that Koplik spots are typically an effect of measles while I am ignorant of this fact. Here, that you treat (i) as evidence for (ii) while I do not is attributable to the straightforward superiority of your background theory to mine: you possess a crucial piece of medical knowledge that I lack. Presumably, if I were to acquire the relevant bit of medical knowledge, then I too would treat (i) as confirming evidence for (ii). The possibility that those who are relatively ill-informed might differ from those who are better informed in the way that they respond to evidence does not itself cast doubt on the capacity of evidence to play the role of neutral arbiter among theories; clearly, what is needed in such cases is for the worse informed party to become privy to those facts of which they are presently ignorant. 