Chapter 2: Methods of Logic

Note of Chapter 2: Methods of Logic from exam perspective.

Chapter 2: Methods of Logic

Method of Logic (reasoning):

Reasoning is the act of ‘using reason to derive a conclusion from certain premise. Reasoning ‘provides’ justification for belief to ‘be true’. Obviously, reasoning is a ‘foundation of truth’.

In general, a distinction is made between reasoning from the general to the particular (deductive reasoning) and reasoning from the particular to the general (inductive reasoning).

1. INDUCTIVE METHOD (Bottom-up logic)

Sometime also called inductive logic, is the process of reasoning in which a general rule is inferred from some set of specific observations.

In inductive inference, we go from the specific to the general. We make many observations, discern a pattern, make a generalization, and infer an explanation or a theory.

This is typically recognized by probabilistic claims in either or both of the premises and conclusions.

In contrast to deductive reasoning, conclusions arrived at by inductive reasoning do not necessarily have same validity as the initial assumptions.

Even if all of the premises are true in a statement, inductive reasoning allows for the conclusion to be false.

Example:

Harold is a grandfather. Harold is bald. Therefore, all grandfathers are bald.
The coin I pulled from the bag is a penny. That coin is a penny. A third coin from the bag is a penny. Therefore, all the coins in the bag are pennies.

2. Deductive method (Top-down logic)

Deductive method is a theory about scientific method. In this method, observations of series of same patterns, or recurring phenomenon or frequency of events, scientific inferences are drawn up. Probability has thus no place in this method.

In deduction, there are attempts to provide sufficient (or conclusive) evidence for the conclusion. Deductive reasoning can be recognized by the structure of the argument and sometimes by the conclusion offered.

This is the method of reasoning in which particular conclusion is derived from general premises. In this case, conclusion is derived with certainty.

Deductive reasoning, or deduction, starts out with a general statement, or hypothesis, and examines the possibilities to reach a specific logical conclusion.

Examples:

All men are mortal. Socrates is a man, therefore Socrates is mortal.
The teachers of KSL teach well. Mrs. ‘X’ is a teacher at KSL. Thus, Mrs.’X’ teaches well.

Differences between deductive method and inductive method:

Inductive method	Deductive method
Developed by Sir Francis Bacon	Developed by Aristotle and Rene Descartes
The method of reasoning in which general conclusion is derived from particular premise is called inductive method of reasoning.	The method of reasoning in which particular conclusion is derived from

	general premise is called inductive method of reasoning.
Bottom up approach. The research begins with specific observation and measure, begin to then detect pattern and regularities, formulate some tentative hypothesis to explore and finally end up developing some general conclusion and theories.	Top down approach. The research starts at the top with a very broad spectrum of information and they work their way down to a specific conclusion.
It is first handed knowledge.	It is readymade knowledge.
Empiricism	Rationalism
Gives new knowledge.	Doesn’t give new knowledge.
Even If the premises are true then the conclusion is only probable and could be false.	If the premises are true then the conclusion cannot be false.
It is method of discovery.	It is method of verification.
Teaching	Discovery
A- posteriori	A- priori
Empirical	Analytical
It is based on probability.	It is based on certainty.
It is pragmatism.	It is formalism.
It has a slow process.	It has a fast process.
More activity	Less activity
It is more open-ended.	It is narrow ended.
Based on observation.	Based on already established principles.
It leads to useful result.	It leads to principle.
It gives teaching.	It gives instruction.
It is an upward process.	It is a downward process.
The source of reasoning is primary.	The source of reasoning is secondary.
Used in our daily life	Used in Courts.

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