WR121 Summer 2010†††††††††††††††††††††††††††††††††††††††††††††††††††††††††††† Michael Dembrow, Instr.





††††††††††† As you know, for an argument to be logically convincing, your assertions (claims) must be backed up (supported) by evidence.Evidence comes in many forms, but in general, we can speak of four large categories:








(4)Expert Opinions


††††††††††† Needless to say, you cannot simply take evidence at face value.It may be that the writer has deliberately or unintentionally used evidence that really is suspect.You, as the reader, recipient, or target of the persuasive argument must be prepared to evaluate the evidence, assess whether or not it is to be believed, judge whether or not it really makes the case.Here are some typical questions that you need to ask:



Is the evidence adequate and representative?

       There should be a number of examples, so that we can see a real trend.

       If a survey, there should be a large enough sample.

       The example, while credible, may in fact be a rare exception.Should we try to change a whole system in order to deal with an isolated problem?


Is it accurate?

       As you look closely at the evidence, do you see any flaws in it?

       While discovering a variety of minor errors does not in itself negate an argument, it does cast doubt on the overall credibility of the argument.

       If the facts in one source contradict evidence that is in other sources, then you must judge the accuracy.


Is it relevant?

       Does it really fit the situation that is being argued?

       Has it been taken out of context?


Is the source of the evidence credible?

       Is the source of the statistics or facts named?

       What kinds of credentials does the expert have (degrees, professional affiliations, employment, experience)?

       Is the source a professional, peer-reviewed journal?

       If a website, who is the owner/author of the website?

       If a website, who is the owner/author of the website?

       If a scientific study, who commissioned it?†† (e.g., a study on health care reform commissioned by the insurance industry would need to be examined very carefully)?

       Does the source of the quotes or statistics have an interest in the matter?

       Generally speaking, if an individual is speaking against his or her interests, the testimony will be more credible.

       Generally speaking, the most credible sources will written by individuals working for academic institutions (though they too may be paid industry consultants on the side), appearing in a peer-reviewed professional journal, or published by a university press.

       Do other credible sources refer to this source?Thatís usually a good sign of credibility (though of course it will not apply to a source that is truly fresh and innovative).

       The more one gets to know about a subject, the more one works with sources related to this subject, the more one will be able to judge credibility.


††††††††††† By the way, evidence is not the only means of supporting an argument, though it is the essential component.The writer can also make good use of analogy (comparing something abstract and unfamiliar with something concrete and familiar) and appeals (ethical/moral and emotional) to move the reader to agreement.Without supporting evidence, though, the argument will fall apart as soon as the reader takes a closer look.


††††††††††† And of course, you, as the writer of an argument, must expect that your reader will be judging you, evaluating your evidence, in the same way.So be careful in your own use of argument.

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