# Thread: Guide to Logic and Constructing Good Arguments

1. ## Guide to Logic and Constructing Good Arguments

I'm writing this guide to teach you the basics of formal logic, what makes an argument strong and some common fallacies. You can use these principles to write essays and other formal writings. This is tertiary level logic.

The Basics
Logic is reasoning conducted or assessed according to strict principles of validity. That is, the construction and/or assessment of the strength of arguments, and there are two different types of logic.

Deductive Logic is an argument that is necessarily true. You can recognize a deductive argument by the simply idea that, if all the premises are true, than the conclusion must be true as well. This means that there must be no new information contained in the conclusion that is not already contained in the premises of the deductive argument. Here is an example of a deductive argument.

Premise 1: All humans are mortal.
Premise 2: I am a human.
Conclusion: I am a mortal.

Since it is true that all humans are mortal, and it is also true that I am a human, it must also be true that I am a mortal. This is an argument that is true by necessity. This is a deductively valid argument, however it is important to note that validity refers only to the logical process behind the argument. It is entirely possible to make a deductively valid argument that makes no sense at all.

Premise 1: Anything that lays an egg is a bird.
Premise 2: Lee lays eggs.
Conclusion: Lee is a bird.

Clearly this makes no sense. Firstly, reptiles also lay eggs, and secondly, Lee doesn't lay eggs and is quite obviously not a bird ... we think. But this argument is nevertheless valid. This is why it is important to assess both aspects of deductive logic; validity and soundness. Validity refers, as I said, to the logical process. Soundness refers to the actual content of the argument. Lee doesn't lay eggs and isn't a bird, so this argument is not sound. But this only applies to deductive logic, and deductive arguments are actually fairly useless. Why? Well, because by their very nature they don't add any new information. Any information contained in the conclusion must be presented in the premises, and if we already know what has been presented in these premises, than the conclusion merely rephrases what we already know. We already know that all humans are mortal and I'm clearly a human. You don't need a logical argument to spell out my mortality for you. Which brings me to the more common and useful aspect of logic.

Inductive Logic is the process of constructing an argument and drawing a conclusion based on evidence. This is the kind of logic upon which science as a whole has been built. Inductive arguments also take the form of premise-conclusion, but unlike deductive arguments, they can't be valid or sound. Inductive arguments are instead strong and cogent. An argument is strong if the conclusion follows probably from the premises, and it is cogent if all the premises are true. If an argument is weak, it is also uncogent. Here is an example of an inductive argument.

Premise 1: The sun has risen every day since the world was formed.
Conclusion: The sun will rise tomorrow morning.

This argument is both strong and cogent. It is a perfect example of what inductive logic does - it uses information about the past to draw conclusions about what is probable. The sun has a very high chance of rising tomorrow morning, but it isn't guaranteed. There are several (unlikely) things which might prevent Earth from undergoing its normal celestial progression, however it's safe to assume the sun will rise, even if you can't be 100% sure. So now you have all this information, what are you supposed to do with it?

Constructing Arguments
Now that you know all about deductive and inductive logic (or at least the bare bones of it), you'll be wanting to put it to some use. Deductive logic can only help you if you're looking to state the obvious, point out the nature of something, etc. Inductive logic can help you write better essays and papers by teaching you how to compose premises for an argument which are both strong and cogent, which in tern will get you good grades, which will land you a better job, which will give you more money. Learning about logic gives you more money! Did you notice what a terrible example of an argument that was? ;D

The very fist thing you need to do when constructing an argument is to decide what your conclusion will be. That is, what is the concept you are trying to support? Once you've chosen your angle, you're going to want to put it into formal terms. So say you wanted to argue the case that child abuse is bad, you might word is like this:

Living in an abusive home has a profoundly negative effect on the physical and mental well-being of children.

- Abused children are in significant physical danger and do not often receive medical treatment for their injuries, which would lead on to talking about
- The death rates among abused children, which would lead to
- Mental/emotional effects as abused children grow up with severe psychological conditions which prevent them from functioning as effective members of the community, which leads to
- Parents who have been abused are statistically more likely to abuse their own children, which leads on to
- The cost to society as this cycle repeats itself through the generations, ergo
C: Living in an abusive home has a profoundly negative effect on the physical and mental well-being of children.

Notice how each point led on to the others? Not every argument will have good fluidity, but there are ways to ease the transition between premises. It's also important to note that I didn't include a justification for why child abuse is morally wrong. This is because a) it is unnecessary, as most reasonable humans would agree that it's wrong to beat your children, and b) touching at length on morality in an argument leaves you on unsteady ground. Why? Because of the next most important thing you will have to do with your argument; defend it before critics.

Every good argument, and every good retortion knows that one of the most important aspects of the inductive process is that of peer review and critique. You may not be able to spot flaws in your own argument, but someone with an opposing viewpoint or perhaps playing devil's advocate for a time may with to challenge certain premises of your argument. This is largely the process by which scientific theories are refined, and while I wouldn't expect it for an undergraduate paper, you can bet your best hat you'll need to defend any research proposals or thesis papers.

It is very important to note that such criticism should both be given and received without any personal attachment. I have turned in research proposals that have been chewed up and spat out by my supervisor, but that doesn't mean he doesn't respect my work and even like me as a person. He does, it just means my work was shoddy and needed improvement. If you are giving rebuttal to an argument, do not make it personal. If you are receiving it, don't take it personally. If you do come across a personal attack, it's one of the most common and frowned upon fallacies.

Fallacies
Fallacies are failures in reasoning that render an argument invalid or weak. The use of any fallacy in formal logic will essentially disqualify your argument from any further consideration, so it's important that you take note of these. So don't use them, okay? Good. Here are some of the major examples.

Ad Hoc, Ergo Proptor Hoc: Say that ten times really fast. xD This is my favorite name for a fallacy, and it's a fairly common one. The translation is "after that, therefore because of that", and is also known as False Cause. It's when two things happening on a similar time frame are claimed to have a cause-effect relationship. "I drank a bottle of orange juice now I have a cold. Ergo, orange juice causes colds." It is important not to confuse the idea of cause and effect with correlation or even coincidence. Some things are unrelated, some things may be related on some level, but it is very rare to find an actual cause-effect relationship.

Ad Hominem: literally "against the man/person", is a category of fallacies involving an attack on the person rather than the argument. The character, circumstances or actions of the person have (in most cases) no bearing on the quality of the claim or argument being made. It is, for example, an ad hominem fallacy to reject anyone's argument based on their ethnicity, religion, sexual orientation, gender, occupation, socio-economic status, etc. It is also a fallacy to reject an argument or claim based on the past actions on

Appeal to Authority: This fallacy is fairly common, and especially in advertising. It is when an "expert" proposes or endorses a claim about which they are not qualified to comment officially. An example would be a golfer giving you advice on which male deodorant to use. Yes, he's a man and he sweats, but the fact that he's a sports person doesn't make him an expert on perspiration and odour control. Be careful of referencing from unqualified sources.

Appeal to Belief: "Oh, everyone knows the French are smelly, therefore the French must be smelly." This is an appeal to what is viewed as a commonly held belief in order to back up your arguments. It also falls under the category of stereotyping or over-generalization and is very unhelpful in formal logic. First off, have you been to France, and second, have you sniffed every Frenchman and woman and determined that they smell bad? Until such an experiment is done, no such claim can be made without becoming an appeal to belief fallacy.

Appeal to Common Practice/Appeal to Popularity: This is similar to the appeal to belief in which the fallacious party argues that a particular action/belief, etc. is morally justified/correct. It should be obvious why this is a fallacy - "If everyone jumped off a bridge ..." Yes, much though you hate that saying, it remains the principle reason this is a fallacy. Just because everyone else is doing it doesn't mean it's right or good.

Appeal to Consequences of a Belief: "I wish that X were true, therefore X is true" or "If X were true, there would be negative consequences, therefore X isn't true." This is known in layman's terms as wishful thinking and should play no part in formal logic. Anyone using this fallacy is really just trying to stick their head in the sand.

Appeal to Emotion/Appeal to Pity: This is usually a fallacy full of emotive language aimed to generate sympathy for a cause based on the feelings surrounding it rather than the actual facts. Ever seen one of those advertisements for animal abuse and rescue shelters? You know the ones set to emotional music with images of abused puppies and kittens with sad faces looking hopefully at the camera while some famous person talks about how you should donate and rescue animals? Yep, that's exactly what this is. So why is this a fallacy? Well, the emotion generated by something has no bearing on whether or not that thing is true or not. Those adverts assure us that every animals in their care has been horrendously abused, when the truth is that a lot of rescue organizations confiscate animals that are perfectly healthy if, say, their owner has failed to register them with the council. Emotions have nothing to do with facts, and it's important to remember that. Not that I'm discouraging people from donating to the ASPCA or other rescue agency. ^-^

Other fallacies of this nature include: Appeal to Fear, Flattery, Novelty, Ridicule, Spite and Tradition.

Begging the Question:
This is where the premises of an argument directly or indirectly claim the truth of the conclusion. Ever heard that old argument that "Person A says they're not a liar, therefore Person A is not a liar." This simply doesn't work, it's a circular argument and fairly pointless.

Biased Sample: This is a fallacy committed when a sample is not representative of a population, or is biased in some way. A good example would be to wander around a pine forest and then declare that all trees are tall with needles and pine cones. A single pine forest is not representative of every tree in the world.

Burden of Proof: This is a big one. Person A says that God exists. Person B says God doesn't exist, so to whom does the burden of proof fall? Well, science says it falls to anyone attempting to make a positive claim, that is, the claim that something is rather than that something is not. If you want to claim that God exists, the burden of proof falls with you rather than with people who wish to make the negative claim that he doesn't. Likewise for those who wish to claim that ancient aliens genetically engineered mankind, or that apples cure cancer.

Composition: The claim that a population has certain characteristics because a member of a population has those characteristics, or that the whole of a thing has such characteristics because the parts of a thing have them. The fact that I like apple crumble doesn't mean it is a logical conclusion that the rest of my family likes it too. Similarly with the pine forest analogy. Not all trees have pine cones.

Division: This is the opposite of Composition, where the characteristics of a whole are applied to its parts or the individuals of a population.

False Dilemma/False Dichotomy: This fallacy is when the argument presents you with what appears to be a dilemma, but which in actual fact has many alternatives which are simply overlooked. "I need to pass this course or my life will be ruined!" is a good example. Either this student passes their course or their life is completely over, however there are other options not being mentioned here. The student may fail the course but still be able to pass their degree, or may choose a different field of study, or go out and get a job. It is not one or the other and should not be presented as such.

Ignoring a Common Cause: I'm sure you've all heard of the ice cream salves/shark attack correlation and people going on about how us eating ice cream makes us tastier for the sharks or something like that. This is the fallacy of ignoring the common cause which, in this case, is summer. Ice cream sales and water temperatures rise, we go swimming more, and more shark attacks occur.

Red Herring: Bringing up an irrelevant topic in order to distract from the origonal argument. You can often see this fallacy committed by polititians.

Slippery Slope: This is the claim that if we allow A to happen, soon B will happen, and then C and all the way to D, E and F, all of which are undesireable things, and therefore we should not let A happen. You often see this argument in matters of morality and law changes as people try to argue that many bad things will come of the change. This is a fallacy because there is no reason to believe one event must inevitably follow another.

Spotlight: This is similar to fallacies of generalization, but occurs when all of a group is judged by those shown in the media to be the primary sample of the group. A good example is the idea that Islam is full of suicide bombers, when that is merely what the media has portrayed. The truth is that the majority of Muslims are peaceful people, and only radical Muslims have given us this false iimpression.

Straw Man: When someone ignores a person's actual position and substitutes a distorted view of their own construction.

So there you have a list of the major fallacies and why they're incorrect. Hopefully by now you've gained enough of an idea of logic to assist you in constructing arguments, writing papers and essays and havig it out with your friends. Get out there and argue!

2. ## The Following User Says Thank You to Foxer For This Useful Post:

zxzero (07-29-2012)

3. Hmm.. seems that it could be useful when your in a debate.
thanks man, read it all ^^

4. I just learned all of this in philosophy!

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