definitions given by modern logicians

 Question. Analyze with example kinds of definitions given by modern logicians.

Answer. There are two ways of classifying definitions. One of these it the method of definition; and the other is purpose of definitions.

On the basis of the method of defining terms, there are four kinds:

1) Ostensive definition: An ostensive definition is known as a demonstrative definition. It consists in pointing out an objec which is to be defined. It can also be regarded as a special kind of definition by demonstration. For e.g.,

a) 'Giant Panda means this animal',

b) 'This is Empire State building'.

Generally, an ostensive definition consists the word 'This' or 'That'. An ostensive definition helps us to understand the most primitive concepts which are indefinable.

But it has certain limitations. We cannot use this where the words do not possess a demonstrative value, where there is nothing to be shown corresponding to a word. Like, we cannot define imaginary things or words like, 'fairy' or 'ghosts' and also we cannot define certain scientific concepts. An object has many qualities, so we cannot say which quality is mentioned by just pointing towards it. It is also unable to define some real things, like, 'personality', 'gravitation', 'energy'.

2) Extensive definition: Extensive Definition is also called as definition by type. It consists in giving examples of the definiendum (thing to be defined) or the examples of the subclasses included in it. For e.g., when we say animal, it means lion, dog cat, elephant etc., we are using extensive definition. An extensive definition explains a word which stands for a class. Thus an extensive definition explains a word by giving examples of things to which it applies. Generally, an extensive definition is not complete, because it is neither possible nor necessary to give examples of all individuals or subclasses included in the definiendum, in all cases. We can easily give examples of seas, oceans but we cannot define words such as bird, boat or building.

It has also some limitations as we can give a satisfactory extensive definition only when the definiendum applies to a limited number of objects. We cannot define the words which do not stand for classes. It does not say anything about nature and properties of a thing, nor does it explicate its conventional meaning.

3) Biverbal definition: In every language, there are words that have similar or even the same meaning. In such cases, when one of these words is used to define the other, we get a biverbal definition. It is attempt to define one word by another word or one phrase by another phrase. The two words that have the same meaning are called 'synonyms'. Hence this definition is also called synonymous definition. For example:

a) Fair means able.

b) Plausible means reasonable.

c) Valour means bravery or Bravery means valour.

In the example 'c' we see that the terms can be interchanged in such definitions.

However, it is very often very difficult to find a simple word that is an exact equivalent of another simple word. This method is both simple and economical but its applicability is restricted.

4) Definition per genus et differntiam: Certain words are names of classes. Members of a class have certain qualities in common. A definition may state these. When it does so, it is an analytical definition. The most commonly used analytical definition is per genus et differntiam definition. In a per genus et differntiam, the definiendum is analyzed by stating its genus and differentia. One of the relations between classes is that of inclusion. That is to say, one class may be included in another class. To take an example, the class of bees is included in the class of insects. In the above example the class of insects is wider than that of bees and is called as 'genus' and class of bee Is narrower than of insects and is called as 'species'. The qualityr or qualities, in which one species differs from the other specie is called its differentia. The differentia of 'bees' is wax and honey. This distinguishes bees from other insects,

It is also known as the 'Analytical Definition' as in this kind the definition contains an analysis of the definiendum. Example are:

a) Man is a rational animal.

b) Triangle is a plane figure enclosed by three straight lines.

c) Baby is a very young child.

On the basis of the purpose of defining terms, there are two kinds:

5) Stipulative Definition: Definition in which we deliberatel assign meaning to a word is called as stipulative definition. speaker is free to use a word or phrase in any sense he likes. The word will mean what the writer or speaker wants it to mean. For example:

i) Whitehead means by 'zero', the class of all empty classes.

ii) Aristotle means by citizen a person who is qualified to exercise deliberative and judicial functions.

In a stipulative definition the writer says that the word shall have such and such meaning. Therefore, a stipulative definition is neither true nor false. However, they may be useful or misleading. It also enable us to avoid vagueness. Technical terms of every branch of knowledge are defined stipulatively. It economizes space, time and thought. Scientific terms like gravitation differential equation are defined by stipulative definitions.

However, stipulative definition can be used to arouse favorable or unfavorable attitudes. Stipulative definition restricts the meaning of a word. In stipulative definition, the definiendum has no meaning prior to the definition Introducing it.

6) Lexical Definition: Definition which reports the meaning of a word or phrase as it is actually used by people is called lexical definition. Lexical definition report how people actually use words. For example:

i) Billion is one thousand millions.

ii) By SMS means Short Messaging Services.

iii) By Ayurveda Indian means herbal medicines.

The term to be defined has its established or conventional meaning. Attempt is made to reduce ambiguity. A lexical definition is either true or false.

Dictionary report how people use words. Therefore, they contain lexical definitions.

Generally, lexical definitions use the analytical method. But they also use the biverbal, ostensive and extensive method. When a dictionary shows pictures of an object, it is using ostensive method. When it clarifies the meaning by taking examples, the extensive method is being used.

Lexical definition is only used to report the meaning of a word.

Lexical definition does not restrict the meaning of a word. In lexical definition, the definiendum has the meaning prior to the definition introducing it.