Tag Archives: critical thinking

Reason

Faulty Premises 1

19 Comments

Faulty Premises Part 1

Last time we discussed how to dissect an argument, by finding its premises and the conclusion. I also spoke briefly about non-sequiturs—something which is known as a logical fallacy. There are many different kinds of logical fallacy, all of which when used weaken the strength of an argument. In this post I will outline some of the more common logical fallacies, not only so that you can spot them in the arguments made by others, but perhaps more importantly, you can spot them in your own.

A logical fallacy is, as the name implies, a use of false logic to support a conclusion. The best way to highlight exactly what a logical fallacy is, is through showing examples of them.

 

Ad hominem

An ad hominem is when something derogatory is said of a person making an argument or holding a position in place of an actual argument. An example of this is as follows:

Creationists are stupid therefore creationism is false.

The statement ‘creationists are stupid’ by itself is not a logical fallacy (though not a particularly nice thing to say), it is only when the derogatory statement is used as a premise for the conclusion that it is a logical fallacy. Even if the statement is valid, it does not follow from it that the conclusion is true, therefore it is a fallacy.

 

Argument from ignorance

(Argumentum ad ignorantiam)

This fallacy is when someone argues the following:

We don’t know that X is false

Therefore X is true

A few common example of this would be:

Science doesn’t know everything, therefore it is reasonable to conclude that the supernatural exists.

Telepathy is possible – we don’t know everything about the human brain after all.

All that can really be derived from an absence of knowledge is the conclusion; we don’t know. A specific area of ignorance does not make a positive claim plausible or even possible. When one makes a positive claim such as ‘the supernatural exists’ or ‘telepathy is possible’, it needs to be supported with positive evidence. An area of ignorance does not allow one to fit anything that one likes into that gap.

 

Argument from personal incredulity

This fallacy is committed when someone states that they cannot believe how something could be true and then uses this to support their conclusion that this is something is false. A common example of this would be the creationist argument:

I do not understand how something as complex as the human eye could have evolved by chance, therefore evolution is not true.

The logical error committed here is that one’s personal inability to comprehend something is grounds for dismissing it. In reality this is not true, and whilst you personally might not be able to understand something, this does not mean that nobody can. In the above example, there have been numerous instances in which scientists have explained precisely how the eye could evolve via gradual incremental steps (I’d recommend Richard Dawkins’ book Climbing Mount Improbable for such an example). ‘I don’t understand X’ means nothing when used as a premise.

 

Post hoc ergo propter hoc

(Correlation does not imply causation)

Post hoc ergo propter hoc is Latin for ‘after this, therefore because of this’. This fallacy is made when someone assumes a causal link between two things simply because one occurred before the other. In formal terms this fallacy is written thus:

X occurred before Y

Therefore X caused Y

An example of this fallacy would be:

Since the MMR vaccine was introduced diagnosis rates for autism have risen, therefore the MMR vaccine causes autism.

The argument is assuming that there is a link between these two events; the introduction of the MMR vaccine and the rise in diagnoses of autism. However these events following each other does not necessarily mean that one caused the other. Therefore in order to accept the conclusion as valid the person presenting the argument would need to demonstrate that there is indeed evidence of a causal link between the two events that extends beyond the fact that one event preceded the other.

There are cases in which correlation does imply causation, however in these cases there is more evidence to support the claim of causation than the fact that the two phenomena occurred around the same time. X occurring before Y by itself is not sufficient grounds for claiming that X caused Y.

 

I shall end this here for fear of rambling on too much. I will endeavour to highlight more examples of logical fallacies in the next few posts of this series. Until then I can point the interested reader towards the following links, should you wish to know more:

Wikipedia’s list of logical fallacies

The Nizkor Project – Fallacies

www.logicalfallacies.info/

I hope you have enjoyed this post. Feel free to respond with any comments, questions, ideas, suggestions, disagreements or whatever in the discussion thread.

Reason

Dissecting an Argument

16 Comments

In my last post I spoke about issues and how to spot them in an argument. This post will follow in a similar fashion, about how to spot conclusions and premises in an argument.

Conclusions

I spoke briefly about how to find conclusions in my previous post. In a sound argument the conclusion should be a statement that follows logically or can be inferred or deducted from the premise(s). Generally these tend to follow what I’d term indicator words such as the following:

  • Therefore
  • Ergo
  • Consequently
  • Thus

Generally the sentences that follow these words are a conclusion to part of, or the entire argument. Of course these words aren’t always used, one might conclude their argument by saying ‘so in conclusion…’ or ‘this shows that…’. With a little practise you should have no problem being able to find the conclusions in someone’s argument.

Premises

Premises are the bulk of an argument, they are the reasoning that supports the conclusion(s) that you make. These can be statistics, facts, examples, logic, refutations of counter arguments, and so on. These are essentially the pieces of information that you wish to use to convince someone that the conclusion(s) you are drawing are valid.

Examples

Here are some example arguments, with the premises in yellow, and the conclusions in red:

In 2011 there were 8,748 alcohol-related deaths in the UK, heavy drinkers increase their risk of liver problems, cancer and other health issues, therefore alcohol should be more strictly controlled by the government.

[sources used: http://www.ons.gov.uk/ons/rel/subnational-health4/alcohol-related-deaths-in-the-united-kingdom/2011/alcohol-related-deaths-in-the-uk–2011.html and http://www.nhs.uk/Livewell/alcohol/Pages/Effectsofalcohol.aspx]

46% of Americans believe that God created humans in their present form, this calls for a great effort to improve science education in the United States

[source used: http://www.gallup.com/poll/21814/evolution-creationism-intelligent-design.aspx]

[NOTE: These arguments do not necessarily reflect the opinions of the author, they merely serve as examples for education purposes]

Non-sequiturs

Sometimes a conclusion will not follow from a particular premise, or series of premises. This is called a non-sequitur (literally meaning ‘it does not follow’). Here’s an example that many of you will be familiar with:

There is no evidence for evolution, therefore creationism is true.

The conclusion does not follow because it excludes the possibility of both evolution and creationism being false.

In order to spot non-sequiturs, it is advisable to read through the premises of an argument, and think about what kind of conclusions could logically be drawn from them (assuming that all the premises are true). If the conclusion differs greatly from the conclusions that you think are reasonable to have drawn from the premises, then it’s likely that this person has made a non-sequitur.

General tips when making arguments

In order to make your argument as sound as possible, there are some important things to consider when coming up with your premises and conclusions. These are: does my conclusion follow from my premise(s)? Are there any logical flaws in my premise(s)? Is there any research/facts that counters my conclusion(s)? Have I cited references for my argument? Are these references trustworthy? What are the counter arguments to my position?

If you continually scrutinize your arguments in such a way, you will inevitably come up with stronger ones. If you find that your argument is flawed in any way, the most honest thing you can do is discard it. That doesn’t necessarily mean changing your position, it might just mean finding better arguments. However, if you find that no arguments tend to support your position, then the most humble thing you can do is change your position, rather than defending it with bad arguments just to maintain your bias.

In my next post I shall look into some ways in which premises can be flawed, misleading or plain wrong.

Any comments, questions, suggestions etc. about this post are welcome in the discussion thread.

Reason

You Have Some Serious Issues

11 Comments

In my first post on critical thinking, I spoke a little about values and how important they are. In the next few posts I’m going to look at the various means by which one can dissect an argument into its composite parts.

The first thing that it is important to get a grasp of when listening to, or reading an argument is; what the hell are they arguing about? The subject matter of the argument is often referred to as the ‘issue’. Sometimes they can be easy to spot because the person states the issue clearly, sometimes they are more ambiguous. To give you more of an idea of what an issue is, here are some examples:

  • Should the USA have stricter gun control?
  • Does creationism have any place in a science class?
  • Do violent video games negatively affect children?
  • Should George Lucas be allowed to make more Star Wars films?

As you can see, the issue takes the form of a question. This question is what the person making the argument is trying to answer. As I mentioned earlier, sometimes this question is not actually mentioned directly during the discussion, but one can deduce the issue from looking at the conclusion of the argument. Here’s an example:

“Many people, adults and children alike suffer with obesity and the health risks that come with it. Therefore junk food should contain similar warnings to those found on tobacco products.”

We can find the conclusion by looking at indicator words, in this case “therefore,” other examples of such words include; ‘thus’, ‘so’, ‘ergo’, and ‘consequently’ etc. These words tell us that the following sentence is likely to be the conclusion of their argument. Now if we look at the conclusion above, we merely have to rearrange the sentence a little to see that the issue is; should junk food contain similar warnings to those found on tobacco products?

This all seems pretty straightforward, and probably obvious to most of you. But there are instances in which people direct a discussion off course by going for a different issue than the original one raised—be it intentionally or unintentionally. This is often called a red herring. An example of this would be a creationist stating; “scientists carried out carbon-dating on newly formed igneous rocks and they came out as forty billion years old” during a discussion about whether creationism should be taught in schools. However, this does not address the issue at hand, rather it is addressing a completely different issue of ‘does radiometric dating provide accurate results?’ (rather badly at that). This merely serves to throw the discussion off course, and for that reason it is useful to be able to derive the issue(s) from the conclusion(s) of a persons argument and see if they match up to the original issue that you began with. If they don’t then you can discard them and politely request that the discussion gets back to the real issue.

There are of course some issues that cover a whole range of sub-issues. Does God exist? For example, also covers issues like what is the nature of evidence? And what are the attributes of God? etc. It is important to keep track of these and to try to make it as clear as possible what these are and how they relate to the original issue in your presentation. Once we begin to learn how to de-construct arguments to analyse their components, we can begin to make much stronger arguments ourselves. Looking for, and clearly stating the issue at hand might seem obvious, but it is important in order to argue with clarity and to begin to see whether someone’s overall argument fits together.

As always, comments, questions, criticisms and suggestions are welcome in the discussion thread.

Reason

Values and Assumptions

9 Comments

For my debut here at the League of Reason blogs, I thought I would make a few posts outlining some thoughts and ideas about critical thinking that I have picked up on my travels. I hope this will generate some interesting discussion. Thoughts, comments, criticisms and suggestions are very welcome in the discussion thread. In this first post I shall discuss values and the assumptions that we all make based upon them.

Every individual you encounter holds a unique set of personal values. In other words, concepts and principles that are uniquely important to them. I shall provide a by-no-means-coprehensive list of a few things that I personally value below to give an example:

  • Truth
  • Kindness and compassion
  • Liberty
  • Knowledge
  • Creativity

I am of course, liable to agree with someone who shares these values on many issues, however if I were to encounter an individual who values concepts and principles that are at odds with my own, we are likely to disagree fervently on many topics.

The reason that this is important is because our values often remain unstated. For example I may argue in favour of the legalisation of cannabis, due to the value that I place on liberty—and thus all of my arguments will be derived from this stand point, however I may never actually state this value outright during a discussion. Thus all my arguments assume that liberty is valuable without actually explaining why.

If we use a typical theistic argument, such as; “I believe in God because I have experienced him working with me in my life, and have spoken to him through prayer.” What values might you think this person has? How do they differ from your own values?

This kind of argument is made from the standpoint of someone who values faith, personal experience, and intuition.

Rather than refuting this argument by saying something like “personal experience is unreliable, and prayer studies have shown that it has no effect,” it might be more worthwhile to question the values this person holds rather than the arguments that are built upon them. Ask them why they value personal experience over empiricism, explain how your values differ from their own and why you think empiricism is more valuable than personal experience. Even if you do not convince them to change their mind, you will at least gain a mutual understanding of each others viewpoint and likely have a more fruitful discussion.

I think it is very important in critical thinking to gain an understanding of values, and to be able to derive these from looking at the value assumptions that people make in their arguments. It is also important to have good arguments as to why you value the concepts and principles that you do, it will make your overall arguments far more solid.

What are your values?