Providing Logical Structures for Argument

Some arguments depend on particular logical structures to make their points. In the following pages, we identify a few of these logical structures.

Degree

Arguments based on degree are so common that people barely notice them, nor do they pay much attention to how they work because they seem self-evident. Most audiences will readily accept that more of a good thing or less of a bad thing is good. In her novel The Fountainhead, Ayn Rand asks: “If physical slavery is repulsive, how much more repulsive is the concept of servility of the spirit?” Most readers immediately comprehend the point Rand intends to make about slavery of the spirit because they already know that physical slavery is cruel and would reject any forms of slavery that were even crueler on the principle that more of a bad thing is bad. Rand still needs to offer evidence that “servility of the spirit” is, in fact, worse than bodily servitude, but she has begun with a logical structure readers can grasp. Here are other arguments that work similarly:

If I can get a ten-year warranty on an inexpensive Kia, shouldn’t I get the same or better warranty from a more expensive Lexus?

The health benefits from using stem cells in research will surely outweigh the ethical risks.

Better a conventional war now than a nuclear confrontation later.

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Analogies

Analogies, typically complex or extended comparisons, explain one idea or concept by comparing it to something else.

Here, writer and founder of literacy project 826 Valencia, Dave Eggers, uses an analogy in arguing that we do not value teachers as much as we should:

When we don’t get the results we want in our military endeavors, we don’t blame the soldiers. We don’t say, “It’s these lazy soldiers and their bloated benefits plans! That’s why we haven’t done better in Afghanistan!” No, if the results aren’t there, we blame the planners. . . . No one contemplates blaming the men and women fighting every day in the trenches for little pay and scant recognition. And yet in education we do just that. When we don’t like the way our students score on international standardized tests, we blame the teachers.

— Dave Eggers and Nínive Calegari, “The High Cost of Low Teacher Salaries”

Precedent

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Arguments from precedent and arguments of analogy both involve comparisons. Consider an assertion like this one, which uses a comparison as a precedent:

If motorists in most other states can pump their own gas safely, surely the state of Oregon can trust its own drivers to be as capable. It’s time for Oregon to permit self-service gas stations.

You could tease out several inferences from this claim to explain its reasonableness: people in Oregon are as capable as people in other states; people with equivalent capabilities can do the same thing; pumping gas is not hard; and so forth. But you don’t have to because most readers get the argument simply because of the way it is put together.

Here is an excerpt from an extended argument by blogger Abby Phillip, in which she argues that the Ebola outbreak that began in 2014 may not follow the same pattern as past outbreaks:

An idea long viewed as an unlikely possibility is now becoming increasingly real: Ebola might not go away for a very long time.

It has never happened before in the thirty-eight-year history of the virus. Every other time Ebola has made the unlikely jump from the animal world to the human one, it has been snuffed out within days, weeks or, at most, months.

This time, though, in Guinea, Sierra Leone and Liberia, the Ebola virus is raging like a forest fire, in the words of several public health officials. And some of them are raising the possibility that the outbreak-turned-full-fledged-epidemic could become fundamentally different from any other Ebola outbreak on record, in that it might stick around.

“What’s always worked before — contact tracing, isolation and quarantine — is not going to work, and it’s not working now,” said Daniel Lucey, a professor of microbiology and immunology at Georgetown University Medical Center, who spent three weeks treating Ebola patients in Sierra Leone and will soon travel to the Liberian capital of Monrovia for another five-week stint.

“In my opinion,” Lucey added, “a year from now, we won’t have one or two cases; we’ll have many cases of Ebola.”

Unlike past outbreaks, in which Ebola emerged in the sparsely populated countryside of central Africa, this outbreak has become an exponentially spreading urban menace.

— Abby Phillip, “This Ebola Outbreak Could Be Here to Stay”

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Unfortunately, the prediction proved to be more accurate than Phillip might have preferred.

You’ll encounter additional kinds of logical structures as you create your own arguments. You’ll find some of them in Chapter 7 on Toulmin argument.