Proving the Thesis - Logic

Proving the Thesis - Logic

Logic

Learning about logical thinking helps us in two ways:  we learn to evaluate and use information better and we learn how to better present information to others to prove our point.  In other words, we learn to think about information we hear or see, and we learn to think better ourselves.

Inductive Reasoning

There are different kinds of reasoning.  Inductive reasoning is logic that draws a generalization from a particular piece of information.  For example, a person who has only seen red colored roses might (erroneously) infer that all roses are red. Inductive reasoning is subject to error since the particular observation is not necessarily representative of a larger group.  Sometimes, this type of thinking causes people to infer that some bad attribute of one in a group exists among all in that group such as seeing one rotting apple in the bag, makes an inductive leap that all the apples must be rotting. Of course, this doesn't really make sense, but people make these kinds of hasty generalizations all the time which is an error in logic.

Deductive Reasoning 

Deductive reasoning is logic that draws a conclusion about a particular situation from a general rule.  This is more likely to result in an accurate conclusion since a general rule usually applies to all situations within its category: All flowers need water; therefore, petunias need water. 

Syllogism

A syllogism is a three-part sequence of reasoned thoughts to draw a logical conclusion: All flowers need water. Petunias are flowers. Petunias need water.

The syllogism consists of a major premise, a minor premise, and a conclusion.  The major premise is the general or universal assumption used to make a logical analysis: All flowers need water.  Note that if a major premise is not accurate, the resulting conclusion will not be accurate although it may be logical.

The minor premise is the assumption pertaining to an example in the major premise: Petunias are flowers.  Note that if a minor premise is not accurate, the resulting conclusion will not be accurate although it may be logical.  The conclusion (logical conclusion) is the resulting logical thought of analyzing the major and minor premise.  Logical conclusions are not necessarily true or accurate since the major premise or minor premise may not be accurate.

Other Terms Related to Logic

  • self-evident – evidence that is apparent by observation or reasoning
  • valid argument – an argument that based on logical analysis of information; not necessarily true
  • sound argument – an argument based on a syllogism that has accurate major and minor premises

Toulmin Logic

Toulmin Logic is a form of logic that uses claim, grounds, and warrant for analyzing the logic of an argument.

  • Claim – the thesis; the point that is to be proved in Toulmin Logic
  • Grounds – the evidence (proof, support) for the claim in Toulmin Logic
  • Warrant – the result assumption of an analysis of claim and grounds in Toulmin Logic.