Critical Reasoning – The Art of Arguments

As one of the three segments of the GMAT’s verbal section, Critical Reasoning is an important piece of anyone’s pre-test preparation. The issue, however, is that often students have no idea how to prepare for it: CR often seems to fall into that category of things where you just have to magically be smart, at least in many people’s imagination.

Learning to excel on CR, then, means learning what CR is actually trying to assess: your ability to see through BS.

Don’t act so shocked! Seeing through poor arguments, seeing the limitations of a plan and understanding how a conclusion can fail are crucial abilities for anyone in a management role – possibly because there are a lot of BS arguments out there to be wary of! Critical Reasoning, then, is the science of identifying where an argument is weak and seeing what would strengthen or weaken it.

The Argument

According to the GMAT, all arguments are composed of three pieces:

  1. The Evidence
  2. The Assumption
  3. The Conclusion

The Evidence is what they tell you is true. The Conclusion is what they want you to think. The Assumption is the bridge between the tow: what would have to be true for the evidence to prove the conclusion.

That ‘bridge’ is crucial: it has to link the the elements of the evidence to the conclusion. Consider the following argument:

Socrates is human, so Socrates will die one day.

Here, the evidence is ‘Socrates is human’, the conclusion is ‘he will die’ – and already half of you are saying ‘so everyone dies’! But that last part wasn’t in the argument, was it? It was left unsaid – because it’s the underlying assumption. So how did we figure it out so quickly? If we’d never heard the argument before, how would we figure it out at all?

Think about the elements in the evidence: we have ‘Socrates’, obviously, and we have ‘human’. Now look at the conclusion: we have ‘Socrates’ and we have ‘death’. ‘Socrates’ is already there in both – but we have some loose ends with ‘human’ and ‘death’! It’s the assumption that has to tie the two together – ‘everyone dies’.

A Harder Example

Now, that was pretty easy, but the approach pays off on harder questions too! Consider this one:

A recent scientific survey found that home-grown tomatoes contain, on average, 25% more vitamin C than do store-bought tomatoes. So, if you have a cold, you’re better off growing your own tomatoes rather than rushing to the supermarket.

What assumptions are we making here? Well, look at the loose ends: the conclusion talks about store-bought tomatoes and supermarkets – not precisely the same, but certainly close enough not to be the focus of our penetrating analysis! We might start asking hard questions about whether the ‘average’ improvement in vitamin C found in the survey would carry over to our own home-grown tomatoes – but on the other hand, there’s no reason here to think that it wouldn’t!

Both of these are very clever responses that the test-makers can use to construct wrong-answer traps: answers that appear to get at these potential gaps in the argument without actually doing anything of the sort.

Instead, let’s consider the big, honking gap that I suspect many of us missed entirely: the conclusion talks about having a cold, but the evidence doesn’t mention this at all! Which begs the question: who said vitamin C is good for colds in the first place? Even if it were – and it isn’t! – there’s no indication in the argument that this is so! Without some evidence to think that vitamin C helps you fight off a cold, this argument is utterly useless!

The secret is simple – the test-maker is counting on you to make the assumption you should be identifying. It’s the things you take for granted, the things you know are true in the real world that make for the best wrong answer traps and missed assumptions.

Learning to interrogate your own assumptions is central to Critical Reasoning – and as an added bonus, it makes better at spotting BS.

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