Back in September I unveiled my first takedown of arguments that I see popping up in online discourse – namely, appeals to “my own research” and “common sense”. I followed that up by expressing my scorn for any assertion that begins with “I believe…”, a statement that is simply a declaration of personal preference and that has no bearing on anyone else. Today’s post continues this series, albeit with a slightly different, more subtle spin.

Have you ever noticed that your nose is the perfect size and shape to hold up a pair of glasses? Isn’t it remarkable that the placement of the ears relative to the nose support the arms of the glasses? How wonderful is the design of the face! Surely this is proof that the human face has a designer.

Of course you’re smarter than that. You know that it’s exactly the other way around – glasses were designed to fit the face. If our noses had been on our foreheads, we’ve have designed glasses to be an entirely different shape. Of course, this says absolutely nothing about the shitty “design” of the eye that makes us need glasses in the first place.

This practice of assuming the truth of your premise and then cherry-picking and distorting facts to fit that premise is a practice I call “backfilling”, although I am sure it has a real name. I use a creationist example here not because it is used exclusively by the religious, but because it is perhaps most obviously and conspicuously on display when people attempt to bully facts into a literalist biblical account of creation. To be sure, everyone (myself included) uses this tactic from time to time. The psychology behind it is pretty obvious – you believe something to be true, and when it is challenged your mind looks for a rational basis for that belief.

This is similar to appeals to “common sense” or statements of belief – we as listeners are exhorted to believe an asserted statement that strains credulity. The important difference between this tactic and the aforementioned fallacies is that at least the veneer of evidence is presented. That is, we are given something that looks like evidence, provided we don’t take too long to actually look at it critically. Sometimes this comes in the form I have presented above, where cause and effect are reversed. Other times it comes from ignoring or failing to recognize confounding factors and thus jumping to an erroneous conclusion (black people must be more prone to commit crimes – look how many of them are in jail!).

The most frustrating form of this tactic I encounter happens when people make statements and then staunchly refuse to define their terms. Not too long ago, I butted heads with one of the other authors at Canadian Atheist, who seems to have some kind of unhealthy obsession with haunting my posts and writing ridiculous nonsense. One of his favourite tactics is to make some blanket statement, and then when you ask him to define what he’s talking about, he retreats into some mushy nonsense that bears a slight resemblance to the word he’s using, albeit a definition that nobody else would agree with. Thus swimming in the water of muddy incomprehensibility, he is free to make ridiculous and unsupported statements to his heart’s content.

There is a danger in using backfilling to support an argument, namely that unless someone already agrees with your premise, your argument will fail to persuade others. It’s easy to find things that will confirm your own beliefs, but as soon as you step outside a sympathetic audience, you’ll find it increasingly difficult to convince all but the most credulous listener. This is why skepticism is such a useful tool to have – it requires someone to actually define their terms rather than just getting away with blanket nonsense and vauge “well everyone knows what X is” statements.

Because it is so tempting to use this technique in an argument you’re not prepared for, we have to be particularly wary of it when we’re talking outside our depth. Similarly, it might require us to go a bit easier on someone when they’re using it. Unless they’re like Joe and they do it on a repeated basis whilst simultaneously accusing everyone else of being ‘irrational’. Then you know you’ve found a professional idiot, and you should adjust your debate style accordingly.

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