Logos

Logos can be thought of as "the logical quality of a speech or text that makes it persuasive" (Source: Purdue University Online Writing Lab). Often this is straightforward - when you read, hear or see an argument, ask yourself if it makes logical sense. Is the reasoning sound? Does the author make any unfounded conclusions? Is she confusing cause and effect or coincidence with causality? All of these can contribute to, or subtract from, logos.

It is very important to note that logos is not necessarily how logical (sound) or accurate (true) the argument is. It is the attempt at logic made by the way the argument is structured. Of course, a sound and true argument is more likely to establish logos, but it depends on the perception of the audience. As noted in the reading above, two common ways of doing this are through inductive reasoning and deductive reasoning. Inductive reasoning takes a specific example or examples, then assumes that a generalization can be made based on that example or those examples. In other words, inductive reasoning goes from the specific to the general. The following are examples of inductive reasoning:

• Every time I forget to water my cucumber plants during the hot part of the summer, they shrivel up and die. I guess cucumbers need water to survive.
• All the storms I've seen blow in from the west, so all storms must move from west to east.
• I had a friend from Switzerland who was really nice, so all Swiss people must be nice.
• After the Obama Administration gave a guaranteed loan to the solar company Solyndra, it failed and the taxpayers lost money. Therefore, all loan guarantees should be stopped because they will lose money.

Inductive reasoning can be correct or incorrect (the first example above is correct, and the other three are not, by the way) - it is up to the audience to determine whether or not the logic is valid. But inductive reasoning is an attempt at logos, irrespective of its validity. The persuasive effectiveness of logos depends on a myriad of factors and can change from audience to audience. The same goes for deductive reasoning. Deductive reasoning is the application of a general belief, and applying it to a specific example, i.e., it goes from the general to the specific. Some examples of deductive reasoning are below:

• Every time I forget to water my cucumber plants during the hot part of the summer, they shrivel up and die. Therefore, if I forget to water my cucumers this year, they will die.
• Every time the gas prices drop significantly, sales of SUVs go up. The price of gas is expected to decrease dramatically this year, so sales of SUVs will increase.
• I've seen hundreds of swans, and they've all been white. Therefore, the next swan I see will be white.

Like inductive reasoning, deductive reasoning can be false (neither of the above statements can be verified, but they can certainly be false), even if they are sound. If I've seen hundreds of swans and they have all been white, then assuming that the next swan I will see will be white is sound reasoning based on my experience, but it may be false because there are other colors of swan out there. Again, it is up to the audience to determine whether or not the logic is sound and/or true, but it is an example of logos either way.

Logos Strategies

As is the case for pathos and ethos, the effectiveness of the rhetorical strategy depends on many factors, and can (in fact, often does) change from audience to audience. With logos, sometimes seemingly sound arguments are neither sound nor true. This is referred to as a logical fallacy. Logical fallacies are encountered all of the time, and you may even use them, accidentally or otherwise. Logical fallacies will undermine your persuasiveness if they are found by the audience, and in turn, impact your ethos as well as your logos. The reading from Purdue linked to previously goes over some of these arguments and provides some examples. There are many possible strategies, sometimes known as "logical appeals," to making a logical argument. Some of them can be seen in the reading below.

Given all of this, which of the examples below are the strongest attempt at logos? Do any of the other sentences exhibit logos?

1. I think solar panels are a wonderful technology, don't you?
2. I have been in the energy business for almost 40 years, including 30 in the oil and gas industry. But like you, I'm a cost-conscious homeowner with bills to pay. I've never seen a technology as potentially game-changing as solar panels. Those things are going to change the world, and better yet they will save you money.
3. Did you know that Tesla Energy will install and maintain solar panels on your roof at no extra cost? You don't have to lift a finger, and you will end up paying less for electricity than you do now. There is no better way to save money and get clean electricity for your home. And all of it is guaranteed by contract! I had them install panels on my house, and couldn't be happier. They'll do the same for you.
4. You know, every time I see that old coal-fired power plant I think of all of the innocent children living nearby that are probably having asthma attacks because of the pollution. That's why I added solar panels to my roof.