No matter what your parents thought, “Because I said so,” doesn’t make for a valid argument, though it may be a persuasive one. A claim, no matter how forcefully asserted, demands evidence. In fact, the more absolute the claim, the more compelling the evidence must be. Otherwise, all you have is an assertion.
Evidence, often referred to as grounds or data, turns an unsupported assertion into a persuasive argument. Evidence makes a claim true or valid. Fortunately for those of us who like to make grand claims, evidence can be found everywhere.
Facts are certainly persuasive… who can argue with hard data or cold reality? All of history, science, and art lie waiting to support the right claims. Quantitative data can be especially compelling, as well as malleable. But avoid depending entirely on factual evidence; a truly effective argument appeals not only to the head but also to the heart.
We value both the wisdom of crowds and the words of authority figures far more than we probably should. But if you’re making an argument, you cannot afford to ignore the persuasive power of social proof. Interviews and surveys are excellent ways to co-opt the support of large groups, while famous quotations and sayings channel the insights of respected authorities.
Connecting with others on an individual level adds credibility to many arguments. Take advantage of the power of personal connections by sharing applicable anecdotes, but don’t expect subjective experience to be enough to support most claims.
To understand how these different types of evidence can be used to support an argument, let’s look to a claim near and dear to my heart:
“Summer is the best season of the year.”
FACTUAL: “Psychological research shows a strong positive correlation between hours of daylight and measurements of mood and satisfaction.”
SOCIAL: “TIME magazine conducts a national survey asking Americans to identify their favorite months. July consistently ranks as the top choice, with August a close second.”
EXPERIENTIAL: “Many of the most cherished memories of my childhood recall summer vacations, family reunions, and weeks at the beach.”
Always be sure to distinguish fact from assumption, inference, or opinion. Evidence that can be challenged becomes a claim which requires its own evidence. Last but not least, note that evidence alone rarely provides sufficient support for a claim: warrants serve as the glue connecting one to the other.