The foundation of an opinion piece -- whether it is an essay or an editorial or a column or a letter to the editor -- is logic. Those who wish to be effective in convincing others of something need to have at least a basic grasp of logic.
Logic, according to James D. Carney and Richard K. Scheer in "The Fundamentals of Logic," is "primarily the study of arguments and of methods to determine whether arguments are correct or incorrect." An argument is a sequence of statements together with a claim. The claim is that one of the statements, called the conclusion, follows in some way from the other statements, called the premises. "An argument is correct when the claim that the conclusion follows in some way from the premises is justified."
There are two basic kinds of logic: formal logic (also called deductive logic or deductive reasoning) and informal logic (also called inductive logic or inductive reasoning).
Formal logic proceeds from the general to the specific. It uses the general to prove the specific. An example: All cats sleep 18 hours a day. Pierre is a cat. Therefore Pierre sleeps 18 hours a day." There is a certainty about formal logic because it uses as its major premise ("All cats sleep 18 hours a day") a universally, or at least commonly, accepted truth. If the minor premise ("Pierre is a cat") is stated accurately, the conclusion is inevitable.
Which is why most of us don't use formal logic much in our daily lives, and why it is of limited value in opinion writing. If there were a huge body of "universally accepted truths," what would we need editorial pages for?
In fact, many of the opinions in letters and editorials that infuriate readers the most are faulty exercises in formal logic in which the writer incorrectly assumes that a premise is commonly accepted. Strip them of their verbal excesses and rhetorical flourishes, and you will find in these pieces the bare bones of a formal argument:
"All men are scoundrels. Bob is a man. Therefore Bob is a scoundrel." Or: "All government spending is foolish. Social Security is funded by the government. So Social Security is foolish."
You will find a whole lot of people (at least half of them) who don't think all men are scoundrels. And a great many people who depend on government in one way or another (that's just about all of us) don't think all government spending is foolish.
Which brings us to informal logic, which is what most of us use in our daily lives, including our contact with editorial pages. Informal logic proceeds from the specific to the general. And where formal logic has some certainty, in informal logic there are only degrees of probability. We know or can observe some specific things, and we can say that these specifics probably warrant a logical conclusion. Informal logic is a generalization based on samples, or a hypothesis based on evidence. How valid the argument depends on how big the sample and how good the evidence.
This is a pretty weak informal argument: "It has rained the last three Mondays. Tomorrow is Monday. It's going to rain tomorrow." This is a better one: "Since records have been kept, it has rained here on Monday 70 percent of the time. Tomorrow is Monday. It will probably rain tomorrow." And here's an even better one: "Whenever the relative humidity has risen at night and hit 82 percent, it has always rained within an hour. The relative humidity has just hit 82 percent, and it is 11:59 a.m. It will rain tomorrow."
Theoretically, the repeated exercise of informal logic makes formal logic possible. If those of us who advance arguments -- editorial writers and letter writers alike -- do it well, we should prove and accumulate a body of commonly accepted truths that can then be used as the major premises of deductive reasoning.
But it can be a long way from major premise to correct conclusion in informal logic.
There are four ways an informal argument can be resolved, only one of them the correct way.
If our facts are right (premises are true) and we use them properly we have an argument that is sound. If we have the facts right but reason improperly, we have an argument that is unsound.
If we have the facts wrong but reason with them properly (it happens often), we have an argument that is valid but unsound.
And if the facts are wrong and we also use them improperly, we have the worst result possible: an argument that is both invalid and unsound.
Would you believe such arguments have actually made it to editorial pages? And not all of them contributed by readers.
