Heusser                                                                                 Philosophy 100                                                             Handout #5a

                                                                                                                                                                                                                       

Argumentation: An Introduction to Reasoning

 

 

I. Arguments: A set of statements, one of which is the conclusion (aka thesis, “main point”) and the rest of which are called the premises (aka reasons, evidence, support, “proof”), in which the premises purport (intend) to prove the conclusion. One of the most important tasks in argument analysis is being able to distinguish premises from conclusions.

 

it follows that                            we may infer                 accordingly       as a result         thus

subsequently                             in conclusion                 consequently     it must be that   hence  

for the reason that                     given that                      in that               seeing that        for

may be inferred from                 since                             in light of           owing to            because

                                   

A. Inductive Arguments: The premises are intended to provide some, but less than conclusive, support. Inductive arguments can be strong or weak. Three Inductive Examples:

  1. Abductive Arguments (also Causal and Inference to the Best Explanation):           

All of us got sick after eating the bratwurst. So, the bratwurst caused the sickness.

  1. Analogical Arguments:          

1.       The government regulating drugs is like a parent preventing a child from playing with a harmful object (i.e. scissors).

2.       Parents should be able to do prevent a child from playing with harmful objects.

3.       Therefore, the government should be able to regulate drugs.

  1. Enumerative (also Statistical Arguments, Generalizations and certain Predictions):

The sun has risen (loosely) every day the last million years. Thus, it will rise tomorrow.

 

B. Deductive Arguments: We expect the conclusion to follow necessarily from the premises. Deductively valid examples include Modus Ponens, Modus Tollens, Disjunctive Syllogism, Hypothetical Syllogism, and Reductio ad absurdum.

A Deductively valid example:

1.       If Clinton is legislating from the White House, then she is President.

2.       Clinton is not President.                                                                              

3.      So, Clinton is not legislating from the White House.

 

Sound Argument: A deductive argument in which the premises do in fact prove the conclusion. This is a test for a sound argument (Sound arguments must pass both tests):

1.       Premises test: Are all the premises true?

2.       Reasoning test: Assume the premises are true. In that case, must the conclusion also be true (i.e. necessarily follow)? Valid arguments pass this test. It is possible for all the premises to be true and the conclusion false in invalid arguments.

 

II. Exercises: Identify the premises (P1, P2, etc.,) and conclusion for the following:

1.       If euthanasia is morally wrong, then the apocalypse is upon us. This is the case because if euthanasia is morally wrong, then there are a lot of corrupt people in our society. And if there are a lot of corrupt people in the world, then the apocalypse is upon us.

2.      Surely whatever I had admitted until now as most true I learned through my senses. However, I have noticed that the senses are sometimes deceptive, and it is wise never to completely trust those who have deceived us even once. Thus, I cannot trust what I have learned through my senses. (Descartes’ Meditations)