Unit 4 of Logic – I (syllabus: Module IV — the purpose of definition; real and nominal, and the modern kinds; the traditional rules of definition and definition in law; logical division, dichotomy and classifying evidence). Below: what the unit covers, the provisions it turns on, and the cases an examiner expects you to name.
What this unit covers
- What is definition, and what purposes does it serve?
- What are the six kinds of definition, and how are they classified?
- What are the four rules of per genus et differentiam definition, and their fallacies?
- What is logical division, and how is it distinguished from other processes?
- What are the rules of logical division and the fallacies of division?
- What is division by dichotomy, and what is it worth?
- How are definition and division related?
- How does the logic of definition apply to a statutory definition clause?
Treat that list as a self-test: recite each topic's rule from memory before you open its cases.
Provisions
- Purpose of definition, s. Module 4, head 4.1
- Modern definitions: kinds, methods and purpose, s. Module 4, head 4.3
- Rules of per genus et differentiam definition, s. Module 4, head 4.2
- Logical division, s. Module 4, head 4.5
- Rules and fallacies of logical division, s. Module 4, head 4.5
- Division by dichotomy, s. Module 4, head 4.5
- The relation of definition and division, s. Module 4, head 4.5
- Definition and law, s. Module 4, head 4.4
Leading cases
- Aristotle
- Aristotle for per genus et differentiam definition; the remaining kinds are the modern logicians' additions
- Joseph
- Aristotle for the framework; the rules as stated are the traditional logicians' formulation
- The laws of Contradiction and Excluded Middle
- Aristotle for the rules; their application to drafting is the practical use made of them here