For the purposes of this post, I am going to make a distinction between symbolic logic and rhetorical logic. Symbolic (or mathematical) logic is a field in mathematics that explores the expressive and deductive power of formal systems. While a fascinating topic, it is highly abstract and not immediately related to the way that people express themselves and make deductions through spoken or written language. For that, we need rhetorical (or informal) logic.
Rhetorical Logic
Rhetorical logic is the analysis of how truth is conveyed through language. Truth is hard to define, but falsehood (especially demonstrable falsehood) is easier to define, so rhetorical logic is usually introduced by teaching the concept of logical fallacies. These are statements that use an argument that is flawed. There are lots of different ways in which an argument can be flawed, but fallacies are usually categorized into two major groups: formal fallacies, or flaws in the form of the argument (regardless of the subject matter of the argument); and informal fallacies, or other kinds of flaws in the argument (usually, but not always, in the content of the argument).Formal Fallacies
Appeal to probability: just because something is likely to happen, does not mean that it will happen. "My small child wandered into the street. He must have been killed." Streets have cars, and cars drive fast. Sometimes cars hit people or animals that wander into the street. However, just because it is possible that a child in the street could be hit by a car, that does not mean that it is inevitable that the child was killed.
The Masked Man Fallacy: "I know who my father is. I don't know who the thief is. Therefore, my father cannot be the thief." The problem is that both premises can be simultaneously true even when they refer to the same person. You do not know who the thief is, and even though you know who your father is, your father might be the thief anyway and you might not know that your father and the thief are the same person.
Some specific types of formal fallacies are propositional fallacies, quantification fallacies and formal syllogistic fallacies.
Propositional Fallacies
Quantification Fallacies
Formal Syllogistic Fallacies
- A is a B; B is a C; therefore A is a C.
- B is not a C; A is a B; therefore A is not a C.
- B is a C; A is sometimes a B; therefore A is sometimes a C.
- B is not a C; A is sometimes a B; therefore A is sometimes not a C.
Informal Fallacies
Post hoc ergo propter hoc (Latin for "after this, therefore because of this"): "The rooster crows, and then the sun rises. Therefore the rooster's crow causes the sun to rise." This can often be more subtle. "I can't help but think that you are the cause of this problem; we never had any problems with the furnace before you moved into the apartment."
Begging the question: "Opium induces sleep because it has a soporific quality." Soporific means sleep-inducing. So it is assuming your conclusion in your premise.
False dichotomy: I deal with this one so often that it drives me nuts. "You are either with us or against us". Never mind the fact that most people are oblivious to the "us" in the previous statement. By reducing the myriad of possibilities by two, and observing that your opponent rejects one, you force them into the other possibility. "I hate how high my taxes are. You are less concerned about your taxes. Therefore you love paying high taxes."
Dicto simpliciter: "If you want to allow chemotherapy patients access to medical marijuana, then why not just legalize all illegal drugs?"
Hasty generalization: "Jane supports Proposition 1. Phil supports Proposition 1. Enrique supports Proposition 1. Trinh supports Proposition 1. Therefore everyone supports Proposition 1."
No True Scotsman: "No Scotsman would ever refuse a plate of haggis!"
"But Angus McClaren just refused a plate of haggis, and his family has been in Inverness for centuries."
"No true Scotsman would ever refuse a plate of haggis."
Cherry Picking: "Abraham is willing to sacrifice his son to God. Therefore, the Abrahamic faiths justify murdering your own child."
Ad hominem: "Why should we listen to Bill's argument about the new budget? You know he cheats on his wife."
Appeal to fear: "A vote for candidate X is the same as voting for the terrorists."
Wishful thinking: "I dislike the incumbent. Therefore, if he is defeated in this election, our lives will be so much better."
Reducio ad Hitlerum: "You want to know who else invested heavily in infrastructure? Adolf Hitler. He built the Autobahn. Still think investing in infrastructure is a good idea?"
Straw Man: So called because one person builds a man of straw and demolishes it, instead of challenging the other person: "We should provide sex education in schools."
"Really? Telling them they can screw around with impunity? Don't you think that's irresponsible?"
The respondent is conflating sex education with an invitation to licentiousness, which is not the same thing as sex education, but easier to refute.
False analogy: using an analogy in your argument that does not sufficiently match the case you are arguing. "There should be a flat income tax. It's unfair to have a graduated income tax. That just punishes rich people for their success. After all, we don't penalize honor students for having good grades." Money exists in an economy. Grades exist in an evaluative educational setting. Grades are finite, whereas money is potentially infinite. The tools of economics cannot describe the fluctuation of grades, since money and grades are too dissimilar. There is an income tax, but there is no tax on grades, so it is comparing things that are qualitatively different.
This should provide a start. Certainly you don't have to learn all these names, or be able to catalog these and other examples, but if you find yourself asserting that a fallacy is true, you are wrong. Basic intellectual hygiene depends on rooting out fallacies in one's reasoning and embracing a clear epistemology. Understand that a scientific epistemology will differ from a philosophical epistemology which will most certainly diverge from a religious epistemology. But when someone asks you: "How do you know that you know what you claim to know," you need to have an answer.
However, I do not assert that reason is the highest possible standard for dealing with the myriad of experiences, impressions and ideas that life has to offer, although it is very high. I can come up with reasoned arguments for and against why I should love my wife, but at the end of the day, I either love her, or I don't. Reason can persuade me to disengage or engage more deeply with her, which might augment or diminish my love for her, but at a given moment, I love her or I don't, regardless of what I think. [I'm not actually married].
Similarly, religious experiences probably cannot be reduced to reason. Certainly, gnosis is an extra-rational experience. Not necessarily beneath reason, but certainly beyond it.
In the USA, we are coming upon another Presidential election, and emotions are high, and much of what passes for reason is actually highly emotive and not very rational. If your argument is: "My proposition is true because I am very emotional about it," you have no argument. If your argument is: "My proposition is morally obvious," then if even one person fails to find it obvious, you need a backup argument that appeals to reason, which if it truly is obvious, should not be that hard to do. Political parties, and more especially political action committees are going to be trying to persuade you to vote for their candidate, and they are not usually going to bother with giving you valid arguments. Be vigilant.
In Hermetic philosophy, reason is symbolized by a sword. A logical argument is similar to a fencing match, with thrusts and parries, and the occasional kill shot. But reason can also be a heavy claymore, or a scalpel, or a poignard, or a bayonet, depending on how we use it. The four elements are earth, air, water and fire, symbolized by disks (or coins), swords, cups and wands in the Tarot. We master the element of earth, with coins, by harmonizing with our bodies, and with the environment, and by figuring out how to earn a living and support ourselves. We master the element of air, with swords, by mastering reason and understanding its role in our lives, and how it is able to overcome folly and error. We master the element of water, with cups, by being able to hold our emotions in suitable vessels, that do not stagnate or fester, but allow our emotions to flow through us, enriching us. We master the element of fire, with wands, by discovering our true wills, and empowering ourselves to exercise our true wills to take up the space we occupy in the universe, and to further our aims. All students of Hermeticism learn to use these tools to master the four elements, and thereby to transcend them and enter higher consciousness.
You should have been taught logic, and especially rhetorical logic, in high school (if not middle school). Chances are, unless you were on the debate team, none of your teachers shared any of this with you. That's tragic, but remediable. Start now. If you Google "fallacy", there are 12.8 million results, including lots of web pages explaining more about fallacies. Please do yourself a favor and spend a few minutes learning about them.
And if you are a Mason, than the study of logic is non-optional for you. From the night you became a Fellow of the Craft you have been beholden to study logic and follow reason. If you no longer feel that logic applies to you, and you no longer want to follow reason, you might want to sit down and seriously consider why you chose a fraternity that values reason so highly, and demands adherence to reason of its members.