being rather fragments of a classification than exhaustive arrangements of the whole matter of argument. The objection which lies, in common, against the best of them is, that they are not practical; they do not group the kinds of evidence under classes truly convenient for instructing and aiding us in the rhetorical work; they state rather dialectical than practical grounds of distinction. It must, of course, be admitted that a correct knowledge of logic is useful and necessary for constructing
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