Informal Logic in a Nutshell: Argument & Argument Analysis

I. Argument
An argument is an attempt to persuade by presenting reasons or evidence in support of a conclusion. It consists of a set of propositions in which the supporting propositions are known as the premises and the supported proposition as the conclusion. The process of drawing a conclusion from the premises is called making an inference.

II. Argument Analysis
The analysis of an argument has two basic parts. A) Identifying and reconstructing the argument so that it is clearly understood and free of rhetorical distractions. B) Evaluating whether it is a good (cogent) or bad argument.

A. Identifying and Reconstructing Arguments
Identifying whether a particular speech or text contains an argument is a matter of determining whether it falls within the definition of an argument. As stated above, an argument is an attempt to rationally persuade an audience of the truth of a conclusion by offering premises in support of it.

With this in mind, we can see that many things within the realm of language are not considered arguments. These often include questions, commands, many insults, compliments, descriptions, explanations and so on.

Example: 
The latest annual inflation rate for the United States is 2.1% through the 12 months ended June 2014.

By itself, this is not an argument but simply a statement used to convey information.

In real world dialogues, it is often difficult to determine exactly what someone's argument is. Perhaps there is a sense that an argument is being presented but it's premises and/or conclusion are unorganized, implied or buried among other elements of the dialogue.

To cut out the clutter and clearly understand just what is being put forward, it is often necessary to systematically reconstruct the argument. When doing so, extraneous material such as rhetorical flourishes, need to be eliminated. Also, premises and conclusions which are implied but not expressly stated need to be clearly written.

When reconstructing arguments, it is important to adhere to the principle of charity. This means that when seeking to understand someones argument, we try to understand it in it's strongest, most persuasive form. To do this, it is necessary to maintain a mindset of trying to reach the truth of the matter instead of one where we are trying to defeat an opponent.

Standard Form
One method of reconstructing arguments is to restate them in standard form. Arguments reconstructed in standard form have their premises listed in the order they occur in the reasoning process and the conclusion listed at the bottom. The premises are usually numbered P1, P2 and so on and the conclusion labelled with a C. A line, called the inference bar, may be drawn between the last premise and the conclusion.

Example:
P1  All humans are mortal 
P2  I am a human 
C  I am mortal

Identifying the Conclusion
When reconstructing arguments it is usually easiest to first identify its conclusion. This can often be done by carefully reading the passage or listening to the speech and determining what point the author is trying to make. What is it they are trying to persuade you to believe?  Also, locating indicator words is a good way to locate the parts of an argument. Conclusion indicators (also known as inference indicators) include "therefore", "as a result", "implies", "hence", "thus", "so", "consequently", "suggests that" and "which means". Note: though indicator words can be helpful in identifying the parts of an argument, they can also appear in context outside of arguments. As such, they should be thought of as a helpful tool but not a guarantee.

Identifying the Premises
To find the premises, ask yourself what reasons are given (stated or implied) which support the conclusion. Just as conclusion indicator words can help you locate the conclusion, premise indicator words may help you find the premises. They include "since", "as indicated by", "as shown by", "because","as", "given that" and "considering that". As with conclusion indicators, these should be thought of as useful tools, not guarantees.

B. Evaluating Arguments 
The goal of evaluating arguments is to determine where they fall on the spectrum of good and bad arguments. A good argument is one where the premises are acceptable, and provide relevant and sufficient grounds for the conclusion. In the realm of informal logic, this is often referred to as a cogent argument.

Evaluating arguments using these three factors can be applied in a two step process of first assessing if the premises are acceptable and then assessing if the premisses are relevant and sufficiently support the conclusion. (see note 1 & 2 below)

It should be noted that a bad argument (one that doesn't pass the requirements above) doesn't necessarily mean the conclusion is false. It just means that the argument as presented doesn't provide a good reason to accept the conclusion (see fallacy fallacy).

1. Assessing if  Premises are Acceptable
Assessing the premises of an argument involves appraising whether it is reasonable to accept them. A premise is acceptable if there is some reason to believe that it is true and no good known reason to believe it is false.

2. Assessing if Premises are Relevant & Provide Sufficient Grounds for the Conclusion
A reasonably supported conclusion is one where the premises are both relevant to and provide sufficient grounds for the conclusion.

a) Relevance refers to premises that provide some evidence or offer reasons that support the conclusion or can be arranged in a way from which the conclusion can be derived. Relevance can be categorized as positive relevance, negative relevance and irrelevance.

When assessing an argument we would say that statement A is positively relevant to statement B if the truth of A counts in favor of the truth of B. In other words, A provides some evidence or reason to believe that B is true.

Statement A is negatively relevant to statement B if the truth of A counts against the truth of B. So if A is true, it provides some evidence or reason to believe that B is not true.

Statement A is irrelevant to statement B if it is neither positively relevant nor negatively relevant to B. In other words, when statement A does not logically support or logically undermine statement B, we would say it is irrelevant.

b) Sufficiency refers to the degree of support provided by the premises to support the conclusion. Whereas relevance is a property of individual premises, sufficiency is a judgement made about all the premises that support the conclusion. Hence, to be considered sufficient, the premises must provide enough support to reasonably accept the conclusion.

Note 1: The order in which the process of evaluating arguments isn't important. You can evaluate the acceptability of the premises first and then evaluate the relevance and sufficiency second or vice versa. 

Note 2: Two handy acronym's for evaluating arguments is Blair and Johnson's ARS (Acceptability, Relevance, and Sufficiency) and Govier's ARG (Acceptability, Relevance and sufficient Grounds).



A Practical Study of Arguments, Trudy Govier
Logical Self Defense, Ralph Johnson & Anthony Blair
Critical Thinking: A Concise Guide, Tracy Bowell & Gary Kemp
Stanford Encyclopedia of Philosophy: Informal Logic
Good Reasons for Better Arguments: Jerome Bickenbach & Jacqueline Davies
The concept of argument, and informal logic, David Hitchcock
On Common Knowledge and Ad Populum: Acceptance as Grounds for Acceptability, David Godden
The truth about truth as a condition of premise adequacy