I was born into a family that constantly had (and still has) discussions on a variety of controversial and debatable topics. Over the years I have had the chance to engage in these discussions in both academic and casual settings. I recently have studied several books on rhetoric, logic and argument and now want to summarize some of the big lessons I have learned. These lessons I believe are essential to having meaningful discussion instead of mindless squabbles.
Rule #1: Don't give conclusions without facts to back it up. Strong conclusions are based on objective facts rather than subjective ones and should be as self evident and obvious as possible. If you can't agree on a conclusion, look at what facts each party possesses and where there is a lack of consensus. A person who does not give facts (aka reasons) for their belief is by definition "unreasonable".
Rule #2: Listen first. Don't go spouting your conclusions and the facts to back it up until you first let others tell you their conclusions and the facts they have in their possession. Ask people "why do you think that" then shut up and honestly and openly listen. Some people may have facts you don't possess. You don't know it all and you should be curious about the reasons other people have for thinking what they do. You don't need to agree, but you should seek to understand others deeply before passing judgement on their point of view.
Rule #3: Acknowledge the strengths of the other sides arguments. Once a person lays out the reasons for what they believe be sure to acknowledge the stronger facts they have given to support their argument. This will show you really are willing to listen and concede when good points are made rather than just fight to win a debate.
Rule #4: Be honest about weakness in your arguments and areas of ignorance. Saying "I don't really know" is a great response. It shows you can be trusted in a discussion. You don't know everything, and some of your own arguments may be based on very debatable facts- acknowledge this. This shows you are honest and more concerned with the truth than your ego or any preexisting biases.
Rule #5: Stop the ad hominem attacks. (ad hominem= "at the man" which is where you attack the person making the argument instead of the argument itself). One of the most common debate tactics is to name call either implicitly or explicitly when you discuss a sensitive topic. For instance, if I make a well supported (but unpopular) conclusion about women, instead of challenging the conclusion and the facts supporting it, the other person might just label me a sexist. Usually the person will not explicitly call you a sexists but will re-frame the debate in a way that makes you defend your personal character rather than the facts presented. (They ask things like "why are you even discussing this?"... implying that you are a sexist even for bringing up those facts) This very common tactic is a way for them to avoid taking on a strong argument they don't like and instead put you on the defensive as you then feel obligated to defend yourself. Another common type of attack is "talking down" do your opponent. This is the art of rhetorically implying some level of intellectual or moral superiority over the other person. You could say something like "You should start with a blank slate and then go where the evidence leads". Which is a way of implying that you start without biases but the other person does not. Good discussion focuses on the conclusions and the facts supporting them, not the person delivering them.
Rule #6: Keep it objective. If God in reality came down today and told you he was going to destroy the earth next Tuesday and you tried to make a case for it you would have a hard time. That is because your experience was a subjective one. It may be totally true, but its hard to have rational discussion based on subjective experiences. In the end we would just have to have trust (have faith) that you were telling the truth. The more objective and the more self evident your facts, the stronger your argument will be.
Rule #7: Don't be an over generalizer. Avoid like the plague words like "Everyone" or "all" or "every time". These suggest there are no exceptions and there are nearly always exceptions. (notice I said nearly to avoid saying "always"). Hyperbole should be avoided in rational discussion. Much better to say "many poor people do drugs" than "all poor people do drugs". Only make absolute statements if you really mean that something is absolutely true in all cases. The best way to avoid the nuance police (see rule 8) is to use statements like "generally", "mostly", "many" and avoid making absolute statements unless you intend to.
Rule #8: Don't be the nuance police. Rarely are things absolute. If I say that men can throw farther than women I am not saying every man can throw farther than every woman in every circumstance. It's obviously more nuanced. However that statement is true in the vast majority of cases and perfectly valid to state. Getting into battles over every possible outlier example is distracting and generally a way for someone to avoid having to acknowledge a valid point. However, it should be remembered it is totally fine to point out nuances if the other person truly intended to make an absolute statement and you want to point out why the conclusion cannot be stated as absolute. The best way to avoid being a nuance cop is to avoid pointing out nuances until the other person has confirmed their intended conclusion has no exceptions.
Rule #9: Anecdotes are generally very weak arguments by themselves. Just because your friend was harassed by a cop does not mean most cops are like that. In order to show that most cops harass people you have to provide objective facts to support the claim that "most" cops engage in harassing behavior. This is not to say anecdotes should be avoided all together. On the contrary they can be used to give emphasis and depth to a conclusion when used in conjunction with other facts but they should generally not be used as stand alone arguments.
Rule #10: Be specific as possible and clearly define things. A clever tactic in debate is to change the meaning of words half way through a discussion if you are losing. Instead of bolstering an argument a person will change the meaning of a commonly understood word like "sexual conduct". Instead of confronting arguments they will say things like "well that depends on what you think constitutes sexual conduct". A way to avoid this is to be specific and even to define key terms in the discussion first. Otherwise you discussion becomes a dictionary lesson with everyone trying to figure out what the heck they are even talking about. No use in discussing things unless you are speaking the same language and using the same definitions.
Rule #11: Focus on facts not credentials. Credentials do matter, but not as much as the facts being presented. What really matters is when a person (with or without credentials) brings new valid facts to the table. We hope people with credentials would be able to provide insightful and relevant facts. However, just accepting a position based on a persons credentials instead of their reasons is a weak form of reasoning. Stronger reasoning is based on excellent objective facts presented by a person with relevant credentials and minimal pre-existing biases. It is key when you bring a source that you actually explain what new facts the source gives us. Just saying a source has reached as conclusion without stating the facts that support that conclusion is a weak form of reasoning. You should not just present a sources conclusions but the relevant facts they bring to the table that support it.
Rule #12: Beware the arguments mismatch. In high school I was shown a video of a young earth creationist preacher with a thick southern accent saying how evolution was not true because the bible said God created the world in 7 literal days 4000 years ago. This was presented as the "opposing view" to evolution. I was then shown top scientists from Americas best universities explaining the theory. This is a common tactic. Match your best arguments with the very worst of the opposition. Beware of this shady tactic. The best way to learn about a divisive issue is to see the best arguments from both sides and always to be looking for better ones from each side. Searching for the best facts from both sides is the best method for making legitimate informed conclusions.
Rule #13: Don't beat up straw men. Just because I say that blacks commit more murders per capita than whites, you should not assume I am saying we should bring back Jim Crow laws. Listen with the intent to understand what the other person means rather than just dissecting his words in an effort to attack him. If you don't understand what a person is trying to communicate ask clarifying questions and listen honestly. Communicate your understanding of the other sides rationale to their satisfaction prior to passing judgement. Assuming you know their argument or falsely interpreting what was said does nothing to further a conversation.
Rule #14: Discover and discuss the root differences. We are almost never going to agree on what good government policies will be unless we first come to a consensus on what the proper role of government is. Discover the root of your lack of consensus before discussing all the other conflicts that stem from that original difference.
Rule #15 Beware of false dichotomies. Not everything is black and white. Don't make the assumption that a situation is either/or. Be open to additional alternatives. However not all alternatives are equally plausible. True dichotomies are situations where there are only are two plausible alternatives.
Rule #16 Measure cause and effect. Here is an example: Fact 5% of cops are racists. Fact 80% of black kids grow up in single parent homes. Which has more of an effect on how graduation rates among black students. Many issues are multi causal. However not all causes are equal contributors to the effect. Just saying something has multiple causes is a weak argument unless the alternative cause can be shown to significant contributor to the effect.
Rule #17 You must show the direction of cause and effect (correlation does not mean causation). For example: People with "can do" attitudes tend to be wealthier. However is this because that attitude produced the wealth or was it the wealth that produced the "can do" attitude. This applies to many cause and effect relationships. It's important to show the logic behind the direction of the correlation not just the correlation itself. Correlation does not imply causality without good supporting logic. It is essential that you not just show that things are correlated but the connection between the two correlated items being discussed.
Rule #18 Beware of humor. Sometimes the best way to avoid confronting an argument is to mock the person making it. Just because something or someone is made to look funny does not mean they are wrong. Facts are better arguments than humor.
Rule #19 Beware the natural fallacy. Did you know that pooping in a toilet is unnatural? Don't assume just because something is more natural it's better than the alternative. Many natural things are good but so are many artificial things (like toothpaste).
Rule #20 Beware the genetic fallacy. This is when an argument is either devalued or defended solely because of its origins. Example one: "But Christianity has been part of our family for hundreds of years!" Example two: "You only believe in Christianity because you were born into a Christian household." Both of these examples say nothing about the validity of Christianity. So if you are having an argument about Christianity these sorts of statements are useless. You could be born into a Christian household and believe in it because of very good reasons. Conversely, Christianity could be a total delusion even though your family believed in it for hundreds of years. An argument should be evaluated based on its merits not on its origins.
Rule #21 Know when a person is using deductive reasoning. Deductive reasoning uses facts to prove a conclusion true or false. (IE. A dog is a mammal. Mammals have warm blood. Conclusion, Dogs have warm blood.)
Rule #22 Know when a person is using inductive reasoning. This is a set of facts that make a certain conclusion more probable. Example: 99 of the 100 males on elm street are convicted child molesters. Here comes George who lives on elm street, conclusion there is a 99% chance he is a convicted child molester. This example does not prove he is a child molester, but it does give a person reasonable certainty if the facts are true about elm street. Often people will attack a conclusion reached by inductive reasoning saying you can't prove it. No conclusion reached by inductive reason is proven, it is merely significantly probable. We uses inductive reasoning and probabilities all the time as we measure risk and rewards in our behavior every day. Don't discredit an argument merely because it can't be proven.
Rule #23 Be consistent. This is the foundational rule for any argument. You can't accept legitimate facts for your argument and then reject legitimate facts that weaken it. To make informed conclusions you must constantly seek all the legitimate relevant facts surrounding an issue.
Rule #24 Explain YOUR OWN logical conclusions, don't drop an expert and run. A common debate tactic is to simply point to an expert (or group of experts) without providing why they are correct in their opinion. Merely stating that an expert agree's with your side of an argument is a very weak form of reasoning unless you are able to explain what substance they bring to the matter being discussed. Having an expert with a similar opinion can be extremely powerful but it is only useful if you can convey what new facts, information or logic the expert brings to the table and why it is relevant. Equally useless is citing an enormous volume of information given by an expert. Telling someone to "read the book" is not conducive to rational discussion as information overload blocks the continuation of a discussion. After all, rational discussion is usually meant to be a discussion about what we have read/heard and what fact WE have gleaned from it. Just telling other people to "read the book" is usually a form of withdrawal from a rational discussion. In the end, anytime you are citing an expert without conveying what great points the expert makes, you are demonstrating your faith in an expert, not your understanding or ability to think critically about an issue.