Argument From Authority
Leading security experts say that every computer should run a complete security suite.
Regrettably, no one has the time, patience, or inclination to become a bona fide expert in every field of study. To compensate for this limitation, we instinctively seek out trusted sources in search of reliable information. But sources are not equally reliable, and some are just plain bunk.
Furthermore, even normally reliable sources get things wrong sometimes, and it's not uncommon for good information from a reliable source to be quoted out of context by some blowhard in an online forum. Since supposedly authoritative sources are subject to error or misquotation, argumentative appeals to authority don't irrefutably prove a given conclusion.
With regard to the example above, we probably could formulate a reasoned argument that every computer should run a complete security suite, but such an argument wouldn't depend on a facile appeal to "experts." Rather, it would take into account demonstrable facts about existing threats and vulnerabilities, and provide evidence that a complete security suite is the best way to protect against them.
I tried Linux once, and it was hard to use. Linux is too hard to use.
We humans make sense of our world by making educated guesses on the basis of the information or experience we happen to have. In psychology, these simple rules of thumb are known as heuristics, and we all seem to be wired to employ them whenever we're faced with uncertainty. Without heuristics, we'd find ourselves paralyzed by doubt and unable to make useful judgments about how to spend our time, money, and energy. And at a simpler level of generalization, we might never draw a useful conclusion from the fact that every time we stick our finger in a fire it gets burned.
The downside of heuristic decision making is that it can lead to hasty generalizations like the one above. In this example, the speaker uses a single experience with Linux to draw an blanket conclusion about Linux. It could be, however, that this person tried one of the more obscure or less intuitive distributions of Linux, or that he tried one with an interface he was unaccustomed to and didn't take the time to learn it. Though we can't fault this person for deciding not to bother with Linux after his first experience, the generalization that the hundreds of Linux distributions in existence are all just like the one he tried is fallacious.
The hasty generalization belongs to a category of logical errors known as inductive fallacies, all of which involve making unwarranted assumptions on the basis of limited information.
A Note About Arguments
For many of us, the word "argument" is fraught with negative connotations. It implies fighting and disagreement, and it conjures up images of angry people bickering with each other. But in logic, an argument is merely a set of statements that support a particular conclusion. In this view, arguing is simply the act of saying something meaningful.
It's almost impossible to state a reasoned opinion about anything without presenting some sort of argument. So you needn't think of arguments as bad things to be avoided. Whether our online interactions are good or bad hinges on how we argue, not on whether we do.
In any debate--online or in person--it's important to assess honestly the facts and arguments we encounter, and to try to understand what others are actually saying. Most flame wars stem from a basic failure to consider the opposing view rationally, or from an assumption that our opponents can't possibly be right (or that we can't possibly be wrong).
If we let rein in our egos and consider the facts and reasoning presented to us, we stand a far better chance of persuading others or--just as important--discovering our own errors. Either way, we win.
Food for Thought
Critical thinking is a learned skill, and it doesn't always come easily, but it's well worth practicing. Armed with an understanding of how logic works (and how it doesn't), we're less likely to be persuaded by nonsensical arguments, even when they're draped in authoritative quotes and appeals to popularity. Better still, developing sound reasoning skills gives us the tools we need to have more useful and interesting discussions about the things that matter to us.
In this article I've touched on only a handful of the many logical fallacies that plague daily conversation both online and offline; there are many others. Fortunately, the Web contains some excellent resources that offer plenty of fodder for your critical mind. Here are a few good sites to peruse:
Wikipedia: This publicly edited encyclopedia takes more than its share of (often fallacious) abuse in the press, but as a reference for critical thinking and logic, it's tough to beat.
Nizkor: Dedicated to countering the irrationality of Holocaust denial, Nizkor is home to an excellent database of logical fallacies.
LogicalFallacies.info: Simple and direct, this no-frills site offers an extensive, well-organized list of logical errors.
The Skeptics' Guide: Created by the New England Skeptical Society, the Skeptics' Guide to the Universe is a popular podcast about science and critical thinking. Its companion podcast, Skeptics' Guide 5x5, offers 5-minute explorations of common logical fallacies and misconceptions.
Robert Strohmeyer is a senior editor at PC World. He tweets as @rstrohmeyer.