Excerpt from Richard M. Weaver’s
Rhetoric and Handbook, Chapter 5


Table of Contents

  1. Introduction: The Enthymeme
  2. Relation of Logic to Rhetoric
  3. The Topics


Although their names resemble each other, the topic comparison differs somewhat from the topic similitude. Comparison involves a relationship which is sometimes expressed by the Latin phrase a fortiori (“all the stronger”). This argument sets up two possibilities, the second of which is more probable than the first, so that if we affirm the first, we can affirm the second with even greater force, or a fortiori. Using this source of argument, we might say, “If a man will steal from his friend, he will steal from a stranger.” When we look at this assertion analytically, we find we are saying that if a certain man, Richard Roe, belongs to that class of men who will steal from their friends, he is at the same time included, and with greater certainty, in that class of men who will steal from strangers. An excellent example of the argument from comparison is the line from Chaucer:“If gold rusts, what shall iron do?” Here the relationship may be expressed as follows: in a situation where gold will rust, it is much more to be expected that iron will rust. Although the explanation of this source of argument is perhaps not as simple as that of the preceding ones, it will be noted that the source is often employed in actual controversy, e.g., “If even honest men are corrupted by office, what can you expect of crooks?”

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