Logic

• Meaning


  The meaning of words, phrases and expressions learned informally as we grow up in different environments
• Definition


  The deliberate explanation of the meaning of words, phrases and expressions
• Meaning and definition are usually treated side by side
• Definiendum


  The symbol being defined
• Definens


  The symbol or group of symbols used to explain the meaning of the definiendum
• Example definition of a rectangle


  • a plain figure enclosed by four straight lines
• Types of definition


  • Stipulative
  • Lexical
  • Ostensive
  • Operational
  • Precising
  • Persuasive
• Stipulative definition


  Used to describe a brand new term when it is first introduced, where the definer has complete freedom to stipulate the meaning
• Lexical definition


  Defines a term that already has an established usage, does not give its definiendum a meaning which is new or different from its established meaning
• Meaning and Definition


  Meaning it already has, not something it hitherto lacked
• Purpose of Meaning and Definition


  Eliminate ambiguity, increase vocabulary, teach how words are used
• Precising Definition


  Reduces vagueness of a term, helps determine if term should be applied to borderline cases
• Theoretical Definition


  Formulates an adequate characterization or scientifically useful description of the object
• Persuasive Definition


  Influences the attitudes of others, usually very emotional, used in politics, religion, advertising, law
• Ostensive Definition


  Defining an object by pointing to instances of such object
• Purposes of Definition


  • Increase vocabulary
  • Eliminate ambiguity
  • Reduce vagueness
  • Explain theoretically
  • Influence attitudes
  • Resolve differences
• Rules for Defining


  • State the essential attributes of the species
  • Must not be circular
  • Must not be too broad or too narrow
  • Must not be expressed in ambiguous, obscure, figurative language
  • Should not be negative where it can be affirmative
• Clarity of meaning of words and expressions is important for students of humanities
• There are at least six types of definitions and many purposes a definition is meant to serve
• When defining terms, the five rules for good definitions must be observed
• Relational statements


  Statements that contain terms that express a relation
• Relational argument


  An argument that contains relational propositions or statements
• Attributes of relations


  • Symmetrical, asymmetrical or non-symmetrical
  • Transitive, intransitive or non-transitive
  • Reflexive, irreflexive or non-reflexive
• Determining validity/invalidity of arguments involving relational propositions


  1. Identify the relational term(s) involved

  2. Identify the attribute(s) of the relational term(s)

  3. Check if the relational term(s) have behaved the way they normally should
• If the relational term(s) have behaved the way they normally should, the argument is valid. If not, the argument is invalid.