INDUCTIVE & DEDUCTIVE REASONING

INDUCTIVE REASONING:

Here, we go from the particular to the general.

Based on observation, facts and experience

Facts are obvious, visible and appealing to common people. Therefore, reasoning based on them would have more adherents.

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Sample studies, case studies, grounded theory, ethnography etc. fall in this category.

Reasoning which takes us beyond the confines of our current evidence or knowledge to conclusions about the unknown.

The premises of an inductive argument support the conclusion but do not entail it i.e. they do not ensure its truth.

Contd.. Induction is used to ascribe properties or

relations to types based on an observation instance

(or on a no. of observations / experiences) It is also used to formulate laws based

on limited obsns.of recurring phenomenal patterns.

Induction is employed in using specific propositions to infer general propositions.

There is strong induction and weak induction

Strong Induction

Consider, Man ‘X’ is mortal Man ‘Y’ is mortal Therefore, all men are mortal

Again, All swans I have ever seen are white Therefore, all swans are white

Another example: This ice is cold (or all ice I have touched is cold) Therefore, all ice is cold

Another example 5+7=12 Therefore, an odd number added to another odd

number will result in an even number

Yet another example: All crows that I have observed are black Therefore, all crows are black

Again, Each time I throw a ball up, it comes back down Therefore, the next time I throw a ball up, it will

come back down

Such conclusions however, are not certain unless we falsify the contrary.

Thus, the truth of the premise would make the truth of the conclusion probable, but not necessary.

Hence the need for a fairly large number of observations and randomness of the sample group for representing the population.

Even so, we conclude with some level of confidence or significance.

Weak Induction

Consider the example : I always hang picture from nails Therefore, all pictures hang from nails

Here, the link between the premise and the inductive conclusion is weak. No reason exists to believe that there are no other ways for pictures to hang. Indeed, not all pictures are hung. Even when hung, they need not be on nails.

Again, Many drivers fined for speeding are teenagers Therefore, all teenagers drive fast

Another example : I usually relax with a cup of tea Therefore, all persons usually relax with a cup of

tea

Here also, the link between the premise and the conclusion is weak. Thus this type of inductive reasoning would lead us to clearly false conclusions or over-generalizations.

VALIDITY

Inductive arguments are never binding but they may be cogent

Inductions are open unlike deductions which are closed

Thus, the conclusion that all swans are white is false; which may have been thought to be true in Europe until the settlement in Australia and New Zealand when black swans were discovered

However, as David Hume argued, our every day reasoning depends on patterns of repeated

experience rather than deductively sound arguments.

Eg. We believe that bread will nourish us because it has done so in the past, but this is not a guarantee that it will always do so.

But then, as Hume said, someone who insisted on sound deductive justifications for everything would starve to death. He advocated practical skepticism based on common sense instead of severe skepticism

DEDUCTIVE REASONING

Here, we move from the general to the particular.

Based on laws, theories and principles. Not so obvious nor appealing to common

people. They are unreal and illusory in

appearance. Thus, reasoning based on them would

have less number of adherents

Examples: All men are mortal I am a man Therefore, I am mortal

Again, According to Newton’s Law, whatever

goes up must come down Therefore, if I throw a ball up, it must

come back down