This difference arises solely because the second subject happens to have another belief that is slightly more justified, not because the belief in p is better supported.
There is one further problem with both of Chisholm’s definitions. Because they both relativize certainty to a particular subject, they make possible the following situation. Two subjects each believe that p, and in each case the belief is justified to degree n. For the first subject, the belief counts as certain because none of her other beliefs have a higher level of justification. But, for the second subject, the belief in question is not certain because she does have another belief that is sl