Despite decades of trying to replace the classic ideas put forth by Aristotle in the book compiled from his lectures and writings, Rhetoric, not one modern theoretician has managed. His basic ideas of how persuasive argument is built has not changed, mostly because they are basic: the proper use of ethos, pathos, and logos create effective and persuasive argument.
Ethos is the root word of ethics, but in this case it refers to the credibility of the author. Is your author an expert in the field he or she is discussing? Yes? Then he or she likely knows what they’re talking about. However. If they can’t express it well–staying focused on their main topic, keeping their writing organized logically, and thoroughly developing it with good choices of evidence and elaborating on exactly how that evidence proves their claims, you’re less likely to pay attention to what they’re saying, and less likely to believe them because of how they’re saying it.
And if their grammar and/or punctuation is poor, you’re even less likely to believe they know what they’re talking about.
In other words, how they present their argument is almost more important to their credibility than their expertise. How else do you explain people listening to Hollywood actors or professional athletes about health issues that they know less about than your average layman?
Now. Apply that to you, and your writing. Think of this: say you’re moved to write a letter to the editor. Say there was an article published in your local paper that you know is wrong, because you’re an unsung expert in the field they’re flubbing. Want to know the best way to build your credibility and get your letter published?
Use your grammar check. Every grammar checker will catch obvious problems (misspelled words, missing punctuation) that would get your letter filed in the circular filing cabinet right next to the editor’s desk.
Pathos is the root word of sympathy, and of empathy. Where writing persuasively is concerned, pathos is appealing to the audience’s emotions. Politicians and tort lawyers love this because it is so very easy to use–and to abuse. John Edwards (former senator and current scumbag) used this hugely in class action lawsuits against obstetricians: he pretended to channel stillborn babies who were supposedly killed by doctors’ carelessness, asserted he spoke for children who were oxygen deprived at birth (again, supposedly because of doctors’ carelessness) and left retarded or with severe cerebral palsy.
It worked. Obstetricians now have to pay astronomical sums for insurance against malpractice because of that particular individual’s efforts in using pathos. Why do you think having a baby costs so much? They pass the costs on to the patients.
Pathos is effective. It’s easy to use. The best and easiest way to use it is to find individual stories–anecdotes–and use them as evidence to support your claim.
Logos is the root word of logic, and is the most difficult tool to use well. Aristotle used it to mean “what is rationally possible”–for instance, in most domestic violence cases, it rarely comes out that half the time, the woman is the instigator. It just doesn’t make rational sense to anyone (except another violent woman) that it could be possible for a five and a half foot tall, hundred and twenty pound woman would attack a six foot tall, hundred and eighty pound man. It just doesn’t make sense, because a rational person knows that that kind of a size difference leads to a bad result…except for when it’s being used in a divorce.
Logos is also the use of hard evidence–facts, statistics, experiments, studies, and anonymous polling results–to support your argument. Convincing the average American of the validity of a position through the use of hard evidence is much, much harder than using their emotions to manipulate them. There is a small minority who actually look for the logical underpinnings of an argument–and that minority is shrinking all the time–however, you cannot convince that minority of your position without it.
And last, but not least, with that minority–your solid use of logos supports and builds your ethos. Your credibility depends upon the evidence you choose, how you present it, and the audience you present it to.
The best arguments have a solid grounding in all three elements.