Key terms and concepts

‘Soundness’ is no longer a mandatory concept but until recently the course has been using the following definition,

This is a fairly standard definition of soundness and it relates the term to deductive arguments and not inductive arguments. Some people would say inductive arguments can never be sound; others would say it is simply inappropriate to apply the term to inductive arguments.

Some books define soundness differently. For example, E. J. Lemmon’s Beginning Logic, a classic introduction to formal logic, equates soundness with validity. It says the following:

It is probably significant that when formal logic is concerned with the manipulation of symbols it doesn’t need to pay too much attention to whether a statement is actually true or false.

Salmon in Introduction to Logic and Critical Thinking, which was first published in 1984 and is now into its sixth edition, applies soundness to both deductive and inductive arguments:

A similar definition is given by Bowell and Kemp in Critical Thinking: A Concise Guide which is a textbook now recommended in the Sept  2018 Course Specification.

Like validity, ‘sound’ has a non-technical use. Someone might say that the piece of wood is sound as opposed to rotten or that the building is structurally sound. Martin Hollis in Invitation to Philosophy, a classic introductory text which is still recommended reading for at least one university course seems to be equating soundness with validity when he says:

but is probably using the non-technical sense for he later says: 

There are good reasons for not including soundness in the mandatory requirements. Although candidates could be asked to define soundness they could not be asked to give an example. If they were, they might write, ‘l’m sitting behind Jeevan so Jeevan is sitting in front of me.’ The examiner can assess this for validity but has no way of assessing the truth of the premise. Similarly, if the candidate is given an argument to assess for soundness it becomes a test of knowledge and to be a fair question the truth of the premises has to be so obvious the question may as well just ask for the definition. It was issues such as these that led to the 2012 question where candidates were instructed to make up a sound argument about a simple diagram:

In everyday arguments the issue isn’t whether the premises are actually true but whether they can be taken as true. This has led some writers to say that when someone says an argument is sound what they are doing is claiming that the premises are true. This is a claim that others may accept or challenge. Kaye in Critical Thinking says: