Flaws

a flaw which says that a small event will cause an extreme result, but gives us no reason to accept that the event and the result are properly linked.

Flawed because the argument goes too far too quickly, unless each link in the predicted chain of consequences can be justified. 

e.g. Even non-violent video games are a danger to your child. They start off peacefully racing cars around a track, avoiding banana skins, but before you know it, they haven't left their bedroom all day because they're addicted to the virtual thrill of shooting inncoent bystanders whilst hurtling around a city in a stolen vehicle. 

when an argument claims that event A caused event B, but actually event A just happened before event B.

e.g. After he started working as a accountant, he lost weight. Therefore calculating tax rebates and looking at company audits is a good way to lose weight.

Also a flaw if it is true/likely that event A caused event B but no evidence is given

e.g. After he stopped having burger and chips for breakfast every day, he lost weight. Therefore, eating a burger and chips for breakfast was making him fat.

an argument where the conclusion repeats one of the reasons.

The reason and the conclusion are the same, so there is nothing to persuade us to believe the conclusion, so we can't accept it.

e.g. It is fair to confiscate his phone because that is a just punishment.

when an argument tries to present its conclusion as the best option by only discussing a limited range of choices. This is also known as restricting the options.

It does not acknowledge more appealing conclusions and doesn't give reasons for dismissing them, so it does not persuade the reader to accept a conclusion.

To demonstrate the flaw, suggest an alternative conclusion.

e.g. Vegetarians are difficult dinner party guests. Either you've got to go to the hassle of cooking a seperate dish for them to disappoint the other guests by not serving meat. I've tried asking them to bring their own food but they seem to find that insulting. I find the best option is just not to invite them. 

a type of flaw where two words or concepts are used as if they mean the same thing when they actually have different meanings. 

It happens when two words have very similar meanings but do not mean the same thing, so saying something is true about one thing does not mean it will be true about the other.

e.g. Mature people make better decisions. I'm older than you,so you should follow my decisions instead of you.

Being mature old and being old is not the same thing, so the reason and the conclusion are about different things, so the conclusion is unsupported. 

when an argument reverses a cause and its effects, saying that the effect brough about the cause.

e.g. Stuart has the flu a lot more than I do. I think it's because he visits the doctor's surgert more often than me. The waiting room must be full of germs and that's why he catches more virus.

It is more likely that Stuart's frequent visits to the doctor are caused by him having flu, not that the flu is caused by his visits to the doctor.

when an argument defends an action by saying that the same action has also been done by other people

The action may be immoral/harmful or nice, but it's still a flaw as it says you should do something just because someone else is doing it.

e.g. All my friends volunteer at charity shops, therefore I should do.

Similar to two wrongs don't make a right - flawed because somebody doing something wrong is not a reason for you to do something wrong.

e.g. I vandalised the politician's garden, but he deserved it because he was corrupt.

when an argument treats sufficient conditions as necessary, or necessary conditions as sufficient.

A necessary condition is something that must happen or be true for something else to be true.

e.g. To be a comedian it is necessary to be funny.

A sufficient condition is something that is enough for something to happen.

e.g. She has a long history of violence against teachers and other pupils, this is a sufficient reason to expel her.

e.g. I am funny, therefore I'll definitely be a comedian, even if I'm terrified of public speaking.

when an argument uses a conclusion about a few things to support a conclusion about lots of things, or everything.

The conclusion is based on insufficient evidence - a claim about two librarians is too specific to tell us anything reliable about all librarians. 

Specific examples illustrate a reason but hasty generalisations use specific examples to support a general conclusion.

e.g. I've only met two librarians in my life, but they were both loud, arrogant and rude. Therefore, I try to avoid all librarians now. 

when an argument misrepresents or distorts a counter argument to make it easier to dismiss.

e.g. Some people argue that it's best for young children if their mothers stay at home, because mothers are instinctively nurturing. But it's clearly wrong to say that mothers are only good at cooking, cleaning and general domestic drudgery. Mothers have all sorts of skills, so they should be allowed to havea career if they want.

By distorting the opposing view, or focusing on one irrelevant weak spot, the argument misses the point and attacks a counter argument that doesn't exist or doesn't matter.

It is flawed because it misrepresents the counter argument, so the counter argument is not properly dismissed.

when an argument tries to get you to dismiss a counter argument or accept a conclusion based on the good or bad qualities of the person arguing, rather than their argument.

The counter argument can still be strong or valid, no matter what the person is like. Ad hominem reasoning is flawed as it gives no reason for dismissing the counter argument.

e.g. Benefit application procedures are too strict. Lady Olivia James argues that we need the procedures to be really strict to make it harder to treat the welfare system, but she's obviously just a rich snob who has no idea what it's like to rely on benefits for survival. 

They can also persuade people to accept an argument because the person is nice.

when an argument's reasons and conclusions are about different things. This is also called arguing from one thing to another.

The reasons and conclusion may be about the same general topic, but not the same aspect of the topic.

e.g. The education system today is entirely focused on how to pass exams. This means exams don't test the full breadth of a students knowledge on the subject, only their knowledge of the specification and assessment objectives. It's no wonder so many A Level students don't know how to use an apostrophe properly. 

when an argument uses a claim about many things to support a conclusion about one individual case.

Just because something is often true or generally the case, it isn't sufficient evidence to tell us anything definite about one specific case, so it's flawed. 

e.g. A lot of rugby players are loud, arrogant and rude. I prefer reserved, polite people. Steve is a rugby player, therefore I won't like him.

When explaining why it is flawed, explain why it doesn't work.

e.g. A claim about many rugby players is used to support a conclusion about Steve. This doesn't work because Steve might be an exception, and no evidence is given to suggest that he's not.