This guide will show you some of the perceptual and cognitive fallacies that you will need to avoid in order to present a sound, logical argument, and which you can identify and attack in the arguments of others. There is a whole lot more to learn than I present here, but if you can apply the principles I detail, you may find it that much easier to persuade someone of your arguments, and once you've mastered this, you can move onto more subtle ideas.
Step One: Know Your Fallacies
Arguably, this is the most important part of constructing a sound logical argument. If you know your fallacies, you can guard against them weakening your own arguments, and conversely, identify the flaws in your opponent's words.
So what is a fallacy? Well simply put, it's a failure in a person's reasoning that exposes their arguments to attack. Though there are a wide variety of possible fallacies, they tend to fall into four general types: logical fallacies, statistical fallacies, extrapolation fallacies, and personal fallacies.
These boil down to a series of steps with an obvious flaw. Most of them are easily demonstrable by silly examples.
All birds are animals. All birds have wings. Aeroplanes have wings. Therefore aeroplanes are animals.
Only men have walked on the moon. I have not walked on the moon. Therefore I am not a man.
As Pirates have decreased in number in the Mediterranean Sea the global temperature has increased. Therefore increasing the number of pirates solves global warming.
Wood is less dense than water, so wood floats in water. Therefore if something floats in water it must have a lesser density. Therefore Wood is less dense than water.
These tend to be down to a misuse of numbers, or human bias. All I can say is beware of numbers; they can be misleading. It is not for nothing that the phrase "lies, damned lies, and statistics" came to be.
With statistics, context is everything. You should be particularly careful about mixing percentages and absolute numbers. For example, a percentage increase is multiplicative when applied to an absolute number, but additive when applied to a percentage - i.e. a 2% increase from 2 is 2.04, which isn't much of a rise; but a 2% increase from 2% is 4%, which is double. Additionally, don't cite numbers if you cannot provide evidence for them; it is the first thing an alert opponent will challenge.
Sample bias refers to the tendency to use unrepresentative samples to illustrate a point about the general population. For example:
99% of the sample polled indicated that they would vote Obama in the next presidential election
Our newspaper's straw poll shows that 80% of the population support position X.
These are attacking an opposing stand by ridiculing it, or extending it to absurdity.
We can't legalize drinking for Teens, because it'll make them delinquents and they won't learn. If they don't learn, then they can't work, putting strain on an already stretched benefits system. The reduction in tax income and increase in spending will harm the economy until it collapses, soon after there will be anarchy and the end of civilization as we know it.
You said this ... which means that ... I attack that stance and imply an attack on what you said..
It's like this or it's like that...
The worst kind of logical fallacies are those used to attack evidence and people rather than arguments. They are not merely fallacious, but as an attack against other people, they amount to offensive insults in lieu of an actual argument.
A scientist argues X, a layman argues Y.
Drawing a comparison between yourself and an authority figure is also a big mistake. You have to justify your argument. Claiming that your qualifications make you immune from challenge or criticism is an automatic loser. In the same vein comparing the opposition to Nazis, Hitler or Stalin are considered argument losers in a big way. Just because Hitler advocated something, doesn't automatically make that specific thing wrong, even if many of the things he advocated were.
The evidence is bad because...
Step Two: Get your Evidence Right
If you're going to argue in posts, I would suggest the following as a way of delivering evidence: Pick out one or two sentences that provide the relevant ideas and allow others to look up the source and read the rest it makes you more credible. This is practical because you are providing the relevant bit from a source rather than just linking for others to look for it, and you're giving the context to show that you're using a source in a non-fallacious manner.
Example: "*points at Encyclopaedia Britannica* it says the universe is 12 billion years old" vs "under astronomy in The Encyclopaedia Britannica (An-Az) it says the universe is 12 billion years old"
(In fact, both of these arguments could be countered in that I might look up a more modern text with a better estimate of, say, 13.7 billion years, however I'd be far more willing to discuss it with someone who can point me to the page than someone who can point me to the right shelf in the library.)
So what is good evidence and what is not? Well good evidence has multiple sources of respectable quality. If you want to argue a point on psychology, one peer-reviewed paper is okay, but having a dozen such studies with the same results is better. Good evidence is also reasonably unbiased. If you're going to look at popular news, you should always ask what the writer/presenter has to gain from the story; papers and news networks will sensationalize stories to get sales/viewers, and many have a political agenda of varying degree. It's not a good idea to put all your faith in a single source - nobody is right about everything - but some evidence is better than no evidence.
Step Three: For the Sake of Balance...
Always try and think from your opponent's view, as it'll help you get to an ending position easier.
Some people like white chocolate as it's sweet and creamy however I understand why people might prefer the rich taste of dark chocolate. Dark chocolate is also a little bitter and hard, I'm not a fan of bitter tastes which is why I prefer white chocolate.
Here I had a list of facts about people's thoughts on chocolate and then I added a justification for which side of the line I fall.
I like to think of making good arguments as if I were making Swiss Rolls; they start on a simple premise and were flat, then I mould them into the shape the maker wanted them to take (rolled it up), and then I deconstruct my own arguments from the perspective of my opponent (unrolled it), effectively picking holes in my own argument. Then I add some new information that let me put my argument back together (like the jam), and I roll the whole thing back up. I then take it apart again (unrolling), before finally adding the last missing piece (the cream), and roll it back together one last time. This leaves you in a very strong position as you've discussed both sides of the argument almost equally and come down on one side of the fence.
Step Four: Writing the Argument
Now you're ready to start writing. Once you have evidence, an outline plan of what to say, and a line of attack; you can put fingers to keyboard. As you write, I suggest you follow these tips:-
- Avoid quote wars; if you're discussing a topic with a group of people, don't turn it into an argument with one person by quoting only them, debunking their work, then waiting for them to argue back. If you end up having a discussion that ignores everyone else's opinions because you and someone else are engaged in a tit-for-tat exchange, then I suggest you stop. Quote wars annoy everyone in a discussion and don't do much to progress a general discussion. If you can't stop quoting, at least move it out of threads and into PMs.
- Don't repeat yourself. Find new things to say, new evidence, and if you need to change your perspective a little, do so. An argument is nothing if not a learning aid.
- Remember to PEE in discussions; make a Point, provide some Evidence and then Explain why the evidence proves your point. It'll make the arguments simple to write and easier to follow, and once you've got it down, you know where fallacies usually turn up (in explanations). Point. Evidence. Explanation.
- If things are becoming difficult to follow, dumb it down and KISS it better. If you can't be concise at least try not to waffle and cloud issues, but at all times think KISS: Keep It Simple, Stupid. Some arguments are unavoidably complex, but don't make an argument hard to follow just because you can.
- Don't get emotional. If you're crying at, or angry with someone, then you've let them win. Take a step back and reread everything, then start your argument again. Ranting or whining won't help you at all.