Writer's WebReasoning: Arguing Cogently
By David Roberts

Academic writing requires writers to make claims and support them using evidence of one kind or another. When writers employ good reasoning, it is called "cogent." As you will see, cogency refers to very specific traits of arguments. Discussed in detail below are the three specific characteristics of good arguments.

Three Characteristics of Good Arguments

A cogent argument has three characteristics, according to Kahane and Cavender (1998):

1. All its premises are true. The premise(s), the reasons for accepting the conclusion(s), must be true – or, at least, believable – in order for the argument to be cogent.

2. It considers all relevant information. Good arguments also consider all information likely to be relevant. This consideration includes addressing counter-arguments and objections to both the premises and the conclusion.

3. It is logically valid. Validity, defined very loosely, means that the premises do, in fact, give readers reason to accept the conclusion the writer puts forth.

A Good Argument and a Bad Argument

Consider the following two arguments. The first argument displays good reasoning and the second demonstrates fallacious reasoning.

1. If it is raining, then the ground is wet.
2. It is raining.
3. Therefore, the ground is wet.

The first premise specifies a conditional relationship. This relationship is denoted by the if/then structure of the sentence. If A happens, then B happens too. This structure is called the major premise of the argument. The second, minor premise of the argument tells us that the “if” part of the first premise takes place. The third statement, the conclusion, then asserts that the “then” part of the first statement takes place as well. This argument form is known as modus ponens.

Now, consider a second argument.

1. If it is raining, then the ground is wet.
2. The ground is wet.
3. Therefore, it is raining.

At first glance, one may be tempted to believe that this argument shows good reasoning as well. Since we have already established the truth-value of the first premise, and since we will assume that somewhere the ground is, in fact, wet, let us consider the relationship between the premises and the conclusion. This argument is invalid: the truth of the premises does not give us grounds to accept the conclusion as true. There are reasons other than rain that the ground could be wet: the sprinkler system could be on, for instance.

Falsely inferring that it is raining because the ground is wet is known as affirming the consequent. This fallacy and others are discussed in greater detail in our logical flaw sections: general inferential errors, errors in causality, errors in generalization, and other fallacies.

The First Characteristic: True Premises

This first condition for a cogent argument is the one likely to involve the most research. An important decision writers must make in their papers is when to take a premise as accepted or whether it needs support from outside research. Judgment in this regard is often formed with experience writing and familiarity with the topic. In any case, many premises will have to be supported in some fashion. See our page on strategies for reasoning and avoiding fallacies for more advice on this topic.

It is also important to identify to your audience that a statement is a premise of your argument. A conclusion often takes the form of a topic sentence; thus, your reasons to accept this conclusion may fall under the umbrella of your topic sentence. You may find it useful to set off your premises with certain phrasings. In your topic sentence, for instance, you could say something as simple as, “X is true for three reasons.” For more information, see our page on writing effective paragaphs.

The Second Characteristic: All Relevant Information Included

Kahane and Cavender (1998) distinguish between including relevant information and establishing the truth of premises. This distinction is not altogether accurate: including relevant information is surely a part of establishing the truth of an argument’s premises. Still, writers will likely find this distinction useful. Specifically, including all relevant information necessitates considering objections to the reasoning of the writer. Including this relevant information thus avoids the problem of one-sided arguments.

Despite the importance of doing so, some may find it difficult to immediately think of possible objections to their arguments. The writing center at the University of North Carolina has three suggestions:

1. Research the topic. Different sources will have different perspectives on the issue.
2. Talk with someone else about your argument. Meeting with your professor or talking to people in your class is a great way to find out possible objections to your argument.
3. Imagine a hypothetical person who denies all of your premises and conclusion. Arguing with this person will enable you to defend your argument against objections. Alternatively, it could also enable you to adapt your stance to accomodate such critics.

Although it is important to address counterarguments in your paper, one must be careful to accurately portray an opponent’s arguments. Failing to do so is a logical fallacy known as constructing a "strawman."

Addressing counterarguments and objections often takes one of the following forms when writing. At the most basic level, addressing these concerns means offering reasons to prefer your own argument to other ones. Addressing objections can involve different types of responses. One could claim that, despite the truth of an objection, one's own argument should still be preferred. Alternatively, one can specifically argue against the cogency (truth or validity) of a counterargument.

The Third Characteristic: Logical Validity

An argument is valid only if it is not possible for all the premises to be true and the conclusion to be false. In the above example of a good argument, it is not possible for both of the premises (that if it is raining, the ground is wet; and that it is raining) to be true and the conclusion (the ground is wet) to be false. This situation is an example of a deductively valid argument. Deductive arguments move from general, broad statements (if it is raining, the ground is wet) to the specific (the ground is wet).

Inductively valid arguments are the opposite. Rather than going from the general to the specific, they work from specific cases and generalize to larger patterns. The truth of such inductively valid arguments is thus much less certain, but it also allows one to reason to genuinely new knowledge. Examples of these arguments often involve experience: we know, or at least believe, the sun will rise tomorrow because it has in the past.

Writers must often use specific words and phrases to identify conclusions they reach in their papers. Words such as “therefore,” “hence,” “thus,” or informally, “so,” often denote a writer’s arrival at a conclusion in his or her argument. These methods of setting off your conclusion help the reader identify the parts of your argument and trace your reasoning.

Works Cited: Kahane, Howard and Cavender, Nancy. 1998. Logic and Contemporary Rhetoric. 8th edition. Belmont, CA: Wadsworth.


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