  The strength of this argument is that it makes use of something indisputable, viz., that Bob's justification is stronger than Ray's; and it is hard to think of any other difference between them except that Bob has felt the heat and Ray has not. On the basis of this case and a number of similar ones, we can generalize to the conclusion that “…every variety of change that brings about or enhances justification either internalizes an external fact or makes a purely internal difference” (ibid., 238).