"Appraising Analogical Arguments" I am self-studying an oldish text on introductory logic by Copi. The text lists some criteria by which arguments by analogy may be judged. Here are three of them: "...the number of respects in which the things involved are said to be analogous." "...the number of disanalogies or points of difference between the instances mentioned in the premisses and the instance with which the conclusion is concerned." "...the more dissimilar the instances mentioned in its premisses, the stronger is the argument." I am confused because the third criterion seems inapplicable to arguments by analogy. This criterion is illustrated by the following example: a particular student is likely to do well in college if ten students of similar background (such as high school grades) also do well, and this argument is strengthened if the analogy involves ten students of different backgrounds. But if the ten other students are of different backgrounds, in what sense is an analogy being made; what is/are the point(s) of comparison? In fact, such an argument seems to be the exact opposite of an argument by analogy, because to argue for the collegiate success of one person based on the collegiate success of a bunch of people whose only similarity to the first is their success in college is to effectively claim that neither background nor anything else effects one's probability of doing well in college. Furthermore, the third criterion does not jibe with the first two.