Critical Thinking
Across the
Curriculum Project

Critical Thinking Core Concepts

Contributed by:  Michael Connelly, Longview Community College

Soundness:

In discussing arguments, we need to distunguish between deductive arguments- arguments where the truth of the premises will guarantee the truth of the conclusion and inductive arguments - those arguments where the truth of the premises will only make the truth of the conclusion highly probable or likely, but not certian.

Another way to identify a deductive argument is to refer to it as a Valid argument. As we read above, Validity refers to the formal structure of the argument- a valid argument is one in which the form is such that:

If it is possible for all the premises to be true and the conclusion to still be false, then you have what is called an Invalid argument. An argument could be invalid and still be a good Inductive argument, or it could be one which commits a Deductive fallacy. Once it is determined that an argument has a Valid form (it is a Deductive argument), the next step is to determine if all of the premises are indeed true. This is done in a variety of ways, depending on the type of premises we are dealing with. The different types of premises are discussed below, but for now, if all of the premises of a Valid argument are true, then the argument is said to be Sound as well as Valid. Only Deductive , Valid arguments can be sound or unsound.

Thus, an argument is sound if and only if :

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Copyright © 1996
Critical Thinking Across the Curriculum Project
Longview Community College , Lee's Summit, Missouri - U.S.A.
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Last modified: 03/02/04