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Symbollic Logic

by Lewis Carroll

“Book 6: Chapter 1”

Additional Information
  • Year Published: 1896
  • Language: English
  • Country of Origin: United States of America
  • Source: Carroll, L. (1896). Symbollic Logic. New York; Macmillan & Co.
  • Readability:
    • Flesch–Kincaid Level: 10.5
  • Word Count: 258
  • Genre: Informational
  • Keywords: math history, mathematics
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BOOK VI.

THE METHOD OF SUBSCRIPTS.

CHAPTER I.

INTRODUCTORY.

Let us agree that “x1” shall mean “Some existing Things have the Attribute x”, i.e. (more briefly) “Some x exist”; also that “xy1” shall mean “Some xy exist”, and so on. Such a Proposition may be called an ‘Entity.’

[Note that, when there are two letters in the expression, it does not in the least matter which stands first: “xy1” and “yx1” mean exactly the same.]

Also that “x0” shall mean “No existing Things have the Attribute x”. i.e. (more briefly) “No x exist”; also that “xy0” shall mean “No xy exist”, and so on. Such a Pro- position may be called a ‘Nullity’.

Also that ”Ü” shall mean “and”.

[Thus “ab1 Ü cd0” means “Some ab exist and no cd exist”.]

Also that ”∂” shall mean “would, if true, prove”.

[Thus, “x0 ∂ xy0” means “The Proposition ‘No x exist’ would, if true, prove Proposition ‘No xy exist’”.]

When two letters are both of them accented, or both not accented, they are said to have ‘Like Signs’, or to be ‘Like’: when one is accented, and the other not, they are said to have ‘Unlike Signs’, or to be ‘Unlike’.