Inductive and Deductive Thinking, Logic and Beliefs

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Hi,

Let's take a closer look through discussion and example:

RESPONSE:

1. Identify and explain one or two beliefs and attitudes of those around you that you believe are founded on poor logic (inductive or deductive). Can you find illogical thinking embedded in cultural beliefs? Please explain.

Many people distinguish between two basic kinds of argument: inductive and deductive. Induction is usually described as moving from the specific to the general, while deduction begins with the general and ends with the specific; arguments based on experience or observation are best expressed inductively, while arguments based on laws, rules, or other widely accepted principles are best expressed deductively. Consider the following example that is not poor logic:

Peter: I've noticed previously that every time I kick a ball up, it comes back down, so I guess this next time when I kick it up, it will come back down, too.

Kelley: That's Newton's Law. Everything that goes up must come down. And so, if you kick the ball up, it must come down.

Peter is using inductive reasoning, arguing from observation, while Kelley is using deductive reasoning, arguing from the law of gravity. Kelley's argument is clearly from the general (the law of gravity) to the specific (this kick); Peter's argument may be less obviously from the specific (each individual instance in which he has observed balls being kicked up and coming back down) to the general (the prediction that a similar event will result in a similar outcome in the future) because he has stated it in terms only of the next similar event--the next time he kicks the ball. (http://www.sjsu.edu/depts/itl/graphics/induc/ind-ded.html).

EXAMPLE: POOR DEDUCTIVE LOGIC

Let's assume Peter said this instead: I've noticed that every time a child let's go of a balloon in a room, it rises to the ceiling, where it remains, so I guess the next time I see a child lets go of a balloon, it will also float upwards to the ceiling, where it will remain.

This is faulty logic because the PREMISES that Peter bases his CONCLUSION ARE BOTH FALSE.

Example 2: Unsound and invalid deductive argument (wrong premise and wrong conclusion):

All wines are whiskey
Chardonnay ...