Thinking Skills: Critical Thinking and Problem Solving

40 Unit 2 Critical thinking: the basics

Commentary

The conclusion is the first sentence. It is

followed by three supporting claims. So in

standard form the reasoning is as follows:

R1 Flying is responsible for ten times the

carbon emissions of rail travel.

R2 Flying is twice as stressful (as rail

travel).

R3 Trains take you to the heart of a city, not

to some far-flung airport.

C Rail travel makes a lot more sense than

short-range flights.

So far [1] and [2] look to have quite similar

shapes: three premises, one conclusion. But

there the similarity ends. In the case of [2]

there is no interdependence between the

premises. Each offers a separate line of

reasoning to the conclusion. In the case of R3,

for instance, the inference that rail travel

makes more sense is made on the grounds that

trains take passengers right into a city centre,

unlike planes. (Actually, this is not always the

case, but it is what the author claims.) True or

not, R3 does not rely on the truth of either of

the other two premises, nor they on it. So,

even if you decide that R3 is not a justified

reason, you can still argue that rail travel

makes more sense on the basis of lower

emissions (R1) and less stress (R2).

So, if you wanted to represent the structure

of [2] in a diagram, you would need three

separate arrows for the three independent

reasons. For example:

R1 R2

C

R3

Indeed, there are grounds for analysing [2] as

three arguments, rather than just one. All

three share the same conclusion, but each one

is a separate line of reasoning.

would not follow from them. (If you want to

check this, try crossing out each of the

premises in turn and see the effect it has on

the argument.)

Structure

The structure of argument [1] can be

represented diagrammatically, for example

like this:

R1 & R2 & R3 C

The single arrow shows that it is the

combination of all three premises that leads to

the conclusion.

In comparison, look at the next argument.

[2] Short-range flights may have become

cheap, but rail travel makes a lot more

sense. Flying is responsible for ten

times the carbon emissions of rail travel

per passenger/km, and twice as much

stress. What is more, trains take you to

the heart of a city, not to some far-flung

airport.

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Activity

Rewrite [2] in standard form, and comment

on the structure of the reasoning.