6a. The law of variation applies only to a series of terms representing notions of the same class or family, the words being arranged in a species-genus order. The increase and decrease of the extension and intension of a series is not proportional.
6b. The law of variation is best explained by using two triangles, one super-imposed upon the other vertex to base and base to vertex.
1a. Employ the following terms in extension――European, flower, term, truth.
{ Russian European { Englishman { Scotchman
{ singular term { distributive { collective
{ Truth has no extension. truth { Since it refers to a { quality only, it is { non-connotative.
1b. Employ the following in extension――grain, rock, soil, precious stone.
2a. Use intensionally bird, quadruped, letter, John.
{ two feet bird { ability to fly { feathers
{ four feet quadruped { back bone { hairy covering
{ heading letter { body { complimentary close
{ John has no intension. John { Since it refers to { an object only, it is { non-connotative.
2b. Use the following in intension――word, table, purity, government.
3a. The use of a term in extension follows when attempting to answer two questions: First, what are the kinds? Second, to what objects may the term be applied? Make application of this with reference to the term _man_.
1. What are the kinds of men? Caucasian, Malay, Mongolian, Ethiopian, Redman.
2. To what objects does the term _man_ refer? George Washington, Chas. Hughes, John Smith.
In both 1 and 2 the word _man_ is used to denote objects, hence it is employed in extension.
3b. Use the term _vegetable_ in extension by answering the two questions in 3a.
4a. Decrease one by one the qualities of some common object with a view of noting how when the intension is decreased the extension is increased.
binding } { leaves } { cover } { school arithmetic printed matter } { designed for instruction } { instruction in arithmetic } {
binding } { leaves } { school arithmetic cover } { school grammar printed matter } { school speller, etc. designed for instruction } {
binding } { school arithmetic leaves } { school grammar cover } { school speller, etc. printed matter } { encyclopaedia } { novel
} { school arithmetic binding } { school grammar leaves } { school speller, etc. cover } { encyclopaedia } { novel } { note book