Logical Reasoning

Logical reasoning is the process of using evidence and reason to arrive at a conclusion. Broadly there are two main types of logical reasoning, deductive (general to specific) and inductive (specific to general).

In deduction, a general rule is applied to a particular case: ‘When it rains, things outside get wet. The grass is outside, therefore: when it rains, the grass gets wet.’ Mathematical logic and philosophical logic are commonly associated with this style of reasoning.

In inductive reasoning, a general rule is found by examining a large number of particular cases: ‘The grass got wet numerous times when it rained, therefore: the grass always gets wet when it rains.’ While they may be persuasive, inductive these arguments are not deductively valid (this is known as the problem of induction). Science is associated with this type of reasoning.

In addition to inductive and deductive reasoning a third category has been proposed called Abductive reasoning, which selects a cogent set of preconditions. Given a true conclusion and a rule, it attempts to select some possible premises that, if true also, can support the conclusion, though not uniquely: ‘When it rains, the grass gets wet. The grass is outside and nothing outside is dry, therefore: maybe it rained.’ Diagnosticians and detectives are commonly associated with this type of reasoning.

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