Wednesday, April 9, 2014

5 minute Logic Tutorial: Deductive Reasoning and Inductive Reasoning

Alright, here's a 5 minute Logic tutorial on Deductive Reasoning and Inductive Reasoning. In formal Logic, these are the two main methods of reasoning.

  1. Deduction- Top-down approach
  2. Induction- Bottom-up approach
The "top" refers to a group or category
The "bottom" refers to an individual or particular instance

You should be able to pick it up as you read on.

Deductive Reasoning

In logic, Deductive Reasoning is known as the "top-down" approach. You go from general qualities of a group to say things about specific instances of that group.

For instance, the most famous example is the "Socrates is a man" syllogism. It goes like this:

(P)All men are mortal
(P)Socrates is a man
(C)Socrates is mortal
You can think of it like this. We have a group of people called "men" and we know a variety of qualities that all people within that group must share: they are mortal, they have a Y chromosome, etc. If we are told that Socrates is a person within that group, then we know that he must share the traits of the group- i.e. that he's mortal and has a Y chromosome.

This is different from Sherlock Holmes' Deduction (Abduction).

Inductive Reasoning

Inductive Reasoning is known as the "bottom-up" approach. It goes from a specific instance (or individual) to reaching grand conclusions about the group they belong to.

For instance, lets say we have Johan, who is a man from country XYZ. If Johan is a smoker and we say that all people from country XYZ are smokers, then we are using induction. Induction.

As you can see, very common use of this is in Stereotyping, where we take qualities from specific instances (in this case, Johan's smoking) , and assume that it applies to all the people of the group the person belongs to (assume that everyone from country XYZ are smokers).

Induction tends to be the riskier and more dangerous form of reasoning.

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