5 ways to use evidence to back up (or challenge) an argument

Drawing: Erin Stevenson O’Connor via Flickr

Based on the material I’m reading and editing, a lot of people have forgotten how to use evidence in their writing. They make unsupported statements that the reader is just supposed to swallow whole. If you want to persuade me that your assessment is valid, your prediction is accurate, or your advice is effective, here are five ways to do that.

Cite a statistic

Nothing persuades like a number. Just make sure it’s relevant to the argument you’re making.

How to use it. Cite the data and the source. To persuade you concentrate on writing better emails, I could tell you that, in my 2016 survey of 547 business writers, they spend an average of 9.3 hours per week reading email, which was 36% of all their time spent reading.

How to poke holes in it. All statistics have weaknesses. Is it out of date? Is the sample too small or unrepresentative? How did they ask the question? And above all, what is the source? I trust unemployment estimates from the U.S. Department of Labor over wild-ass guesses from Donald Trump, for example.

Provide an example

If you’re making a bold and forward-looking claim, there may not yet be any statistics. So cite an example — who else did this and why did it work? (And unless you’re writing a personal narrative, citing examples from your own life or career are far less effective, because we know you’re biased.)

How to use it. Make the claim, then show how it works in practice. “A disruptive technology can destroy a market in less than three years — that’s what happened in San Francisco, where Uber has completely undermined the taxi market.” Several examples are better than one. Prominent people and large companies are more persuasive than random people and tiny companies. Direct quotes from a personal interview are best, but quotes taken from published articles are also effective.

How to poke holes in it. Examples sound more persuasive than they actually are. Can you site a counterexample? Show that the example is not typical?Or show that the cited example doesn’t prove the point the writer is making?

Use an analogy

If something you’re predicting has never happened before, what has happened that is similar?

How to use it. Draw a parallel. For example, “You might think we wouldn’t trust autonomous vehicles. But investors have learned to trust algorithms to gain profit, and we’re all trusting Facebook to tell us what news to read. When machines do things better than people, eventually we learn to trust the machines.”

How to poke holes in it. Is the analogy really relevant? To subvert an analogy, show why the current case is different from the one cited.

Show alternatives are absurd

In the classic mathematician‘s reductio ad absurdum, you start by positing that you are wrong, then show what the awful consequences would be.

How to use it. You must take up a contrary position plausibly and without contempt and calmly reason to an undesirable conclusion. “OK, suppose we did allow South Korea to have nuclear weapons. How would we make sure they didn’t get into the wrong hands? And if they ever used them against North Korea, could we be certain that China would not retaliate? It seems an awfully risk way to save a few dollars.” (By the way, there is a very quick way to make these types of arguments — it’s called sarcasm.)

How to poke holes in it. You can attack the reasoning. But it’s often simpler to show that there is a false dichotomy — that there more alternatives than the one the writer is arguing for and its absurd opposite.

Cite an authority

This is the weakest way to back up an argument, but if the authority is sufficiently believable, it can help.

How to use it. Quote somebody. “As Malcolm Gladwell explains, it takes 10,000 hours for someone to become really adept at a skill.”

How to poke holes in it. Easy. Just cite evidence of the other four kinds that supports a counterargument.

And here are some ways not to argue

Social media, the internet, and comment sections have surfaced a lot of really bad ways to argue. They may make you feel good, but they don’t persuade anybody of anything (except that you’re more emotional than logical). If you’re an honorable writer, please don’t use these:

  • Ad hominem. “But of course, he’s a pedophile and a liar.” Even if it’s true, this doesn’t invalidate his argument. You’ll have to tell me why he’s wrong, not just why he’s bad, or a fascist, or a communist, or a Justin Bieber fan.
  • Guilt by association. “That’s what all those fascist kooks say.” I don’t care who else says it, I care if it’s right. Awful people say true things all the time.
  • Of course we all agree. Everyone has assumptions. Other people may not share yours. Reasoning from shared assumptions fails if the reader doesn’t share your assumptions.
  • Shouting. Profanity, using all caps, and exclamation points don’t make arguments stronger. They show that you have nothing to say.

There are countless other ways to argue inappropriately, but you get the idea. Argue the facts. Argue the logic. Try to leave the personal qualities of the writer out of it. Because if you’re the writer, you wouldn’t want people to treat you that way.

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.


  1. This is all good stuff. Except — and you knew an except was coming — when bad argumentation starts with bad thinking, as it so often does. People who have thoughts that are poorly reasoned can employ all of these things to their own satisfaction and are impossible to convince of their poor thinking. It follows from the availability heuristic: “See, I can easily list Josh’s 5 things to support my point of view.” The fact that they can so easily list multiple things, no matter how poorly reasoned, causes them to bolster their assessment of each individual item so that when you point out the flaw in any one, they resist your reasoning because they obviously have overwhelming evidence. I admire your efforts to improve human argumentation, but this is the one rare place in my otherwise optimistic disposition where I am a pessimist. Now, if we could just fix thinking…