Critical thinking for Students Read Online Free Page B

inference from claims that make up an explanation. This explanation is concerned with (presumably) changes in medical knowledge. These changes could be detailed to include greater understanding of genetic diseases and how to slow down the ageing process.
     
    There will be big changes in medical knowledge over the coming years which will enable us to cure far more diseases than we can at the moment, and which will mean that ageing can be very much slowed down. So, there is a baby already born today that will live until it’s 250 . .
     
    Here’s another prediction.
     
    In 500 million years’ time, there will be no plant life on Earth.
     
    The prediction is again based on an explanation, this time that the Sun has been getting progressively hotter for millions of years and will continue to do so, such that its heat will eventually make plant life (and thus all life) on Earth impossible.
     
    The prediction could then be used to support an inference.
     
    In 500 million years’ time, there will be no plant life on Earth. So, at some point in the distant future, we have will have to abandon Earth and move to live on a different planet.
     
Explanation → Prediction → Inference
     
    We’ll keep returning to this link between claims, explanations, and inferences. But, for the rest of this chapter, we’re going to focus on the process of inference itself.
     
    You’ll remember that we represented the process of inference as claim → claim. The arrow sign shows that the second claim is being drawn from the first. Take out the arrow sign and we have just two separate claims. This shows the importance of the relationship between the two. It also shows that there is an important thing going on. Whoever draws the inference is saying that the first claim is enough for the second one to be drawn. We’ll be coming back to this point time and time again throughout the book.
     
    We’ll now look at some examples of inference.
     
    The need for people to hug each other in today’s world is understandable. So it is good that so many young people, both boys and girls, hug each other.
     
    This is based on a letter to The New York Times in May 2009. Because we have the second claim drawn from the first, we have inference. In other words, we have an argument. The author is arguing that it’s good that young people hug each other because there is an understandable need for people to hug each other. This shows that we can turn round the argument, without the direction of inference being changed.
     
    It is good that so many young people, both boys and girls, hug each other, because the need for people to hug each other in today’s world is understandable.
     
    In this way, we can see that, however the direction of the inference is presented, the argument as such remains the same.
     
    Interestingly, we have here another example where the argument flows out of an explanation.
     
    Following 9/11, school shootings, and other tragedies that we see time and time again in the media, young people are increasingly aware of the fragility of life, of their own mortality. As a result, the need for people to hug each other in today’s world is understandable. So it is good that so many young people, both boys and girls, hug each other.
     
    The first sentence is an explanation (as used in the letter), and it’s used here as support for the second sentence. In other words, we have here an example of
     
    Claim (explanation) → claim (inference from explanation) → claim (inference from inference).
     
    You can see how arguments can be built up, step by step.
     
    Here’s another argument on the same subject (based on another letter):
     
    Physical touch is an important human need. So it is good that so many young people, both boys and girls, hug each other.
     
    In this argument, the same inference is drawn from a different claim.
     
    By the way, you will have noticed that we’ve used the word ‘argument’ time and time again. At no