Critical thinking for Students (13 page)

The judge’s argument is an interesting one. What he does is to use one line of reasoning. This is to say that ‘if growing tomatoes is not seen as a nuisance, then neither is growing cannabis’. As you can see, he is not making any judgement of whether or not smoking cannabis (or selling it to others) is acceptable. His comment is only about growing it.

The judge is using what we call an
analogy
. This is a common form of argument. In essence, it amounts to using an evidence-claim. In this example, the judge takes the evidence-claim that tomato-growing is not seen as a nuisance. Because, he argues, this is the case, we can infer from this that growing other things sufficiently similar to tomatoes is acceptable. Since growing cannabis is sufficiently similar, then it is acceptable to grow it.

We could represent the argument as a syllogism.

As with our previous examination of a syllogism,
if
the reasons are true, then so is the conclusion, making this argument a valid one.

In any evaluation of an analogy, we have to consider the degree of similarity between the two parts. This will be particularly significant when, as in the judge’s argument, an argument based only on an analogy stands or falls depending on this degree of similarity.

The organisation Christian Aid ran a campaign in 2009 in which they claimed ‘For every excuse not to end poverty, we have 10 bright ideas why we can’. One of these was an analogy. (You should be able to evaluate two of the other ‘bright ideas’, in the light of what we were doing in the previous section on ‘appeals’ – ‘Over 70% of us think poverty eradication is important’, and ‘the United Nations Secretary-General has categorically stated that it can happen’.)

The ‘bright idea’ analogy was ‘it’s a big task, but no bigger than ending slavery and putting a man on the moon’. Just like the tomatoes and cannabis analogy, the claim here is one of similarity: that the achievement of these two big things shows that we can achieve this other big thing. If we put it into an argument form, we get the following:

You will probably see that there’s a big assumption needed in this argument. This is that ‘the abolition of poverty is no more difficult than was ending slavery and putting a man on the moon’. In any analogy we always have this assumption of sufficient similarity. Without it, the argument cannot work.

So our task is to see if this assumption can be supported. The first problem is that, unfortunately, slavery has not been ended. The Anti-Slavery Society makes the point that, though slavery as we normally think of it was abolished in the nineteenth century, it is still practised in various parts of the world today (including Africa). Though the number of slaves is disputed, depending on the definition used, the estimates put the number at around 3 million upwards.

With regard to putting a man on the moon, this was (as most people would accept) achieved in 1969. However, it might be argued that, though it was very difficult and so a hugely impressive scientific and technological achievement, it was not as difficult as ending poverty. For one thing, it did not depend on the co-operation of the government of every country in the world (which ending poverty would). For another thing, the definition of ‘putting a man on the moon’ is a straightforward one. The definition of ‘poverty’ is anything but simple: if poverty is ended, does no one go hungry any more? Do certain diseases disappear? Is all housing at least adequate? And yet another thing: would the ending of poverty require a huge redistribution of wealth away from the rich to the poor both between and within countries? Would people like Roman Abramovich agree? Would the Saudi Royal Family agree?

Our problem, as we have seen, is that ending poverty is certainly a bigger (and less clear-cut) task than putting a man on the moon. In addition, in that slavery hasn’t yet been abolished, we can’t say whether it
can
be abolished (and thus whether the difficulty-level of its abolition is sufficiently similar to that of ending poverty). As a result, since the analogy (or, more accurately, the analogies) does (do) not work well, the argument falls. (This last point, of course, refers to an argument like the tomatoes and cannabis one in which the analogy is the only reason. If it is only one of at least two, then the argument might still stand.)

We have seen with our fairly detailed analysis that we need to treat analogies in the same way that we treat any other evidence-claim. Is the analogy relevant? Is it sufficient for the argument? To do this, we need to focus on similarities and dissimilarities.

What follows is a detailed look at an analogy, by going through an evaluation step by step. The argument is one used by someone who was head of the UK’s Youth Justice Board.

What is the analogy?

This analogy compares the problems that will follow putting children who commit crimes in prison with those that will follow building more coal-fired power stations.

What is its function in the argument?

It provides the only reason for the conclusion that we should lock up far fewer young people than we do.

Does the analogy work?

As we have seen, answering this question involves asking other ones:

Are there any other aspects of the analogy that need to be considered?

The two situations are similar (although not in the way the author intends) by both providing benefits. Coal-fired power stations provide electricity, and prisons provide security for the public. Both provide employment. Both provide investment in the future (reformed criminals and industrial etc. progress.) In this way, the support which the analogy gives to the conclusion is lessened.

Which of the two is greater – the similarities or the differences? This is a difficult question to answer and we might disagree. I think that, on balance, the differences are greater but there are very interesting similarities. In that the argument relies only on the analogy, the argument is therefore vulnerable to the charge that there are important differences between the two.

It needs to be remembered that, when someone is using an analogy in an argument, we can’t respond by saying ‘you can’t say that: the two things aren’t the same’. Of course, they’re not
the same
. If they were the same, there wouldn’t be an analogy!

All we have is a circular relationship, not an analogy.

Sometimes you’ll come across a different version of using an analogy.

In this example, we have NASA using what’s called a disanalogy. As you can see, this takes the negative form of an analogy: this is not like that, so…

You might like to look at this disanalogy in the same way that we looked at the analogy on children in prisons (comparing the similarities and dissimilarities), but this time looking to see if the dissimilarities outweigh the similarities. However many you find on either side, it’s pretty clear that they will. In this example, the disanalogy is part of an argument in which it isn’t just a question of an analogy-type reason being used as the reason to draw the conclusion. The argument can be seen in the following way: 

You can see that, in this argument, the disanalogy is not necessary for the argument. If it wasn’t there, the conclusion could still be drawn. (You might have spotted the assumption that ‘trips to Grandma’s house normally succeed’.)

Using analogies is, in an important way, yet another example of the importance of consistency in argument. Someone using an analogy in an argument is saying ‘here’s one situation in which
x
is the case; here’s another in which
x
also applies/follows/exists, so we should do the same in both situations’. Any demonstration that the two situations are not sufficiently similar weakens this argument for consistency. (With a disanalogy, of course, the process is the other way round: the more similar the two situations are, the less powerful is the argument for inconsistency.)

We can also see analogous reasoning as an example of a particular type of reasoning. The author is saying ‘if this happens in a given situation, then the same thing should happen in the other situation.’ This type of reasoning is called
hypothetical
reasoning
. However it is expressed, it will have an
if
…
then
form. (It could, for example, be ‘were this to be the case, then …’) We’ll now look at such reasoning in more detail.

You will remember that we saw an example of this type of reasoning when we looked at slippery slopes. We saw there that there was a problem with the move from the first ‘if’ to the final ‘then’, as shown in the example we looked at.

This showed that with hypothetical reasoning, the connections do need to be justified (as with the controlled climb). Let’s look to see if we can use hypothetical reasoning to go somewhere undesirable but in a justified way, rather than slithering down a slippery slope.

As you can see, there are two hypothetical parts of the argument. The first sentence is the first part, and shows that the form of the hypothetical is sometimes reversed (
x
, if
y
). The second sentence is the second hypothetical. The conclusion is drawn from both of them. You can see that the conclusion is justified all the way. (Of course, this does not mean that there aren’t assumed steps in the argument. A crucial one sits between the second reason and the conclusion: ‘solutions to food and other shortages will not be found’. For example it could be that scientists will be able to create food crops which need little water.)

You will have seen that hypothetical reasoning, when it extends from one such reason to another, is like a chain, with the links connecting in a necessary way to the conclusion. Not surprisingly, then, they are sometimes called ‘chain arguments’. Here’s another one on the same subject of the problems of population growth:

You can see the way that the chain is created. We can focus on it by labelling each section:

Though we might want to evaluate the argument (in terms of possible issues with C and D), the chain sequence is clear. In case you spotted the assumption between B and C that ‘the TV programmes would be good enough to keep people watching’, Mr Azad has got there before you, calling for India’s TV channels to provide high-quality programmes.

Having seen hypothetical arguments in action, it is time to enter a cautionary note. Look at the next example:

You will have noticed the hypothetical argument-chain in the second sentence. There is no problem with this: if A, then B; if B, then C. What should have followed was if A, then D: if herbal remedies work, then (people need to be told) they will have
side-effects
. Instead, this link in the chain is missing. The author draws a conclusion which is not in a hypothetical form. Given that the rest of the argument is in this form, this should not be done. Perhaps herbal remedies don’t work after all, in which case the conclusion cannot be drawn.

So it is important to remember that reasons that are no more than hypothetical require a hypothetical conclusion.

There’s another point to mention. We have seen that hypothetical arguments use a form of ‘if … then’ reasoning. But this does not mean that every time we see an ‘if’, we’ve found some hypothetical reasoning.

You can see that, in this example, the ‘if’ is not part of a hypothetical, in that there’s no ‘then’ that follows it.