Division — Logical division — rules and fallacies of division — Division by Dichotomy. (Kinds of evidence)

Sort every piece of evidence in a case file into ‘oral’, ‘documentary’ and ‘important’, and a sharp opposing counsel will immediately object — not because the categories are wrong, but because they were built on two different bases at once, so a single important oral document falls into two piles simultaneously. Logical division is the discipline that catches exactly this kind of sorting error before it reaches a courtroom.

In two minutes

Logical division is the process of separating a genus (a class) into its constituent species on the basis of one single distinguishing attribute (the fundamentum divisionis), such that the species are mutually exclusive and together make up the whole genus; division by dichotomy is the special case that splits a class into exactly two classes, one having an attribute and the other its plain negation.

The rest of this chapter

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