Definition and Examples of Evidence in Argument

In argument, evidence refers to facts, documentation or testimony used to strengthen a claim, support an argument or reach a conclusion.

The evidence isn't the same as proof. "Whereas evidence allows for professional judgment, the proof is absolute and incontestable," said Denis Hayes in "Learning and Teaching in Primary Schools." 

Observations About Evidence

• "Without evidence to support them, any statements you make in your writing have little or no value; they're simply opinions, and 10 people may have 10 different opinions, none of which is more valid than the others unless there is clear and potent evidence to support it." Neil Murray, "Writing Essays in English Language and Linguistics," 2012
• "When conducting empirical research, the researcher's primary responsibility is to provide evidence to support his or her claim about the relationship between the variables described in the research hypothesis. T]he researcher must collect data that will convince us of the accuracy of his or her predictions." Bart L. Weathington et al., "Research Methods for the Behavioral and Social Sciences," 2010

Making Connections

David Rosenwasser and Jill Stephen comment on making connections that leave out the steps that lead to them in 2009's "Writing Analytically."  

"A common assumption about evidence is that is is 'the stuff that proves I'm right.' Although this way of thinking about evidence is not wrong, it is much too limited. Corroboration (proving the validity of a claim) is one of the functions of evidence, but not the only one. Writing well means sharing your thought process with your readers, telling them why you believe the evidence means what you say it does.

"Writers who think that evidence speaks for itself often do very little with their evidence except put it next to their claims: 'The party was terrible: There was no alcohol' -- or, alternatively, 'The party was great: There was no alcohol.' Just juxtaposing the evidence with the claim leaves out the thinking that connects them, thereby implying that the logic of the connection is obvious.

"But even for readers prone to agreeing with a given claim, simply pointing to the evidence is not enough." 

Qualitative and Quantitative Evidence

Julie M. Farrar defines two kinds of evidence in "Evidence: Encyclopedia of Rhetoric and Composition," from 2006.

"The mere presence of information does not constitute evidence; the informative statements must be accepted as evidence by an audience and believed by it to be relevant to the claim at issue. Evidence can be generally classified as qualitative and quantitative. The former emphasizes explanation and description, appearing continuous rather than discrete, while the latter offers measurement and prediction. Both kinds of information require interpretation, for at no time do the facts speak for themselves."

Opening the Door

In "Evidence: Practice Under the Rules" from 1999, Christopher B. Mueller and Laird C. Kirkpatrick discuss evidence as it relates to trial law.

"The more far-reaching effect of introducing evidence [in a trial] is to pave the way for other parties to introduce evidence, question witnesses and offer argument on the subject in attempts to rebut or confine the initial evidence. In the customary phrase, the party who offers evidence on a point is said to have 'opened the door,' meaning that the other side may now make countermoves to answer or rebut the initial evidence, 'fighting fire with fire.'"

Dubious Evidence

In "Not on the Doctor’s Checklist, but Touch Matters" from 2010 in The New York Times, Danielle Ofri discusses findings called evidence that isn't actually valid.

"[I]s there any research to show that a physical exam -- in a healthy person -- is of any benefit? Despite a long and storied tradition, a physical exam is more a habit than a clinically proven method of picking up the disease in asymptomatic people. There is scant evidence to suggest that routinely listening to every healthy person’s lungs or pressing on every normal person’s liver will find a disease that wasn’t suggested by the patient’s history. For a healthy person, an 'abnormal finding' on a physical exam is more likely to be a false positive than a real sign of illness."

Other Examples of Dubious Evidence

• "America must not ignore the threat gathering against us. Facing clear evidence of peril, we cannot wait for the final proof, the smoking gun that could come in the form of a mushroom cloud." President George W. Bush, in justifying the invasion of Iraq in 2003
•  "We have it. The smoking gun. The evidence. The potential weapon of mass destruction we have been looking for as our pretext of invading Iraq. There's just one problem: it's in North Korea." Jon Stewart, "The Daily Show," 2005