Introductory Logic Lesson 3 - Extension and Intension

What happens to extension as you work up and down a genus and species chart?

As you work your way up a genus and species hierarchy, the extension of each term increases. As you work your way down, the extension decreases.

What happens to intension as you work up and down a genus and species chart?

As you work your way up a genus and species hierarchy, the intension of a term decreases. As you work your way down, the intension increases.

What is the relationship between extension and intension?

Extension and intension are inversely related. As extension increases, intension decreases. As extension decreases, intention increases.

Extension

The extension of a term is the sum of all of the individual things to which the term applies. Think extend...you make it bigger and bigger to include more things. Increasing extension means increasing abstraction (the more abstract, the harder it is to imagine..more of an idea rather than an actual object).

Intension

The sum of the common attributes of a term is the intension of a term. Increasing intension means increasing concreteness (the more concrete, the more easily imagined).

What is the intension of the term "book"?

having pages, on which words are written, which are bound together by some means

What is the extension of the word "marsupial"?

kangaroos, wallabies, koala, possums, opossums, wombats, Tasmanian devil, and more

What is the extension of the term "mammal"?

marsupials, carnivores, rodents, and much more

What is the extension of the term "book"?

novels, dictionaries, textbooks, manuals, and more

What is the intension of the term "mammal"?

warm-blooded, vertebrate, gives live birth, feeds young by milk from females, has hair or fur

What is the intension of the word "marsupial"?

warm-blooded, vertebrate, gives live birth, feeds young by milk from females, has hair or fur, young carried in a pouch