A Class Room Logic: Deductive and Inductive, with Special Application to the Science and Art of TeachingMcNair, George Hastings
Philosophy
A Class Room Logic: Deductive and Inductive, with Special Application to the Science and Art of Teaching
McNair, George Hastings
Logic
That the enumeration must be in terms of its distinguishing or
characteristic attributes is implied in the derivation of the term
_definition_. The attributes must establish limits or bounds, just as a
line fence limits a land owner’s possessions. To indicate that man is a
creature possessing the power of locomotion, sense of sight and ability
to eat, is surely not a definition, as the marks are not characteristic
of men only. These attributes set no boundary between man and horse,
consequently the statement is a faulty _description_ of man, not
a _definition_. But when the enumeration includes such attributes
as power of speech, rationality and ability to laugh, then does the
description become a definition. To put it differently: A definition is
a description of a term by means of its distinguishing attributes. This
statement may be considered a definition of man, though somewhat faulty:
“A man is a creature who is rational and who possesses the power of
speech and ability to laugh.”
=4. DEFINITION AND DIVISION COMPARED.=
We have learned that general terms when connotative may be used
extensionally or intensionally.
A definition indicates the _intensional_ nature of a term, while a
statement which points out the _extensional_ nature of a term is known
as logical division. More briefly: A definition is an _intensional_
statement of the nature of the term, while logical division is an
_extensional_ statement of the nature of the term.
To illustrate: The following statements are definitions:
(1) A dog is a domesticated quadruped of the genus canis and given
to barking.
(2) A quadrilateral is a rectilinear figure of four sides.
(3) Soil is a substance composed of pulverized rock and decayed
vegetable matter in which plants will grow.
The following represent Logical Division:
(1) Dogs are divided into hounds, terriers, bull, etc.
(2) The kinds of quadrilaterals are trapeziums, trapezoids and
parallelograms.
(3) The various soils are loam, sand, clay, muck, etc.
=5. THE KINDS OF DEFINITIONS.=
Generally speaking there are three kinds of definitions, namely,
(1) Etymological, (2) Descriptive, (3) Logical.[5]
(1) _An etymological definition is one based upon the derivation of the
term._
This kind of a definition, which gives merely the meaning of the
symbol, is sometimes called a _nominal_ or verbal definition; while
a _real_ definition is regarded as one which gives the _meaning
of the notion_ for which the symbol stands. The modern logician is
inclined to ignore this classification on the argument that to make a
distinction between a symbol and the notion it symbolizes is simply to
misunderstand the relation which exists between them. If the definition
does not agree with the thing then it cannot correctly explain the
term which represents the thing. Define correctly the term and one has
defined correctly the notion signified by the term.
Public-domain text, read in full here on John Shaqi.
A Class Room Logic: Deductive and Inductive, with Special Application to the Science and Art of Teaching — John Shaqi
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