Critical Thinking Handout 2 Can you prove it? An example in critical thinking ‘Proof’ is an important concept in critical thinking. We want pupils to be able to decide whether or not a statement someone has made is justifiable. If we ask someone to ‘prove’ something then we are asking them to justify their statement. This would normally be understood to be a good question to ask when thinking critically as you are not accepting something at face value. But consider the following examples: Can you prove that the area of a circle is πr2? Can you prove that water contains hydrogen? Can you prove that the earth has moving tectonic plates? Can you prove that perestroika led to the collapse of the Soviet Union? Can you prove that Abai wanted Kazakhstan to look to the west? Each of these is a good example of ‘thinking critically’ as someone who asks these questions is not accepting an answer at face value. However, how would someone go about finding out the answer to those questions? The problem here is that the word ‘proof’ means something different in each case. Question Can you prove that the area of a circle is πr2? What kind of proof? Mathematical proof Explanation Mathematical proof can be proved by tautology, by showing there are no exceptions, geometrically, and so on. Can you prove that water contains hydrogen? Scientific proof (in chemistry) Can you prove that the earth has moving tectonic plates? Scientific proof (in geology) Can you prove that perestroika led to the collapse of the Soviet Union? Historical ‘proof’ Can you prove that Abai wanted Kazakhstan to look to the west? ‘Proof’ in Literature In many sciences proof is made by experimentation: an experiment is created in which the hypothesis (water contains hydrogen) is tested. It is hard to create experiments to test the theory of tectonic plate movement (evolution is another good example) are plate movement cannot be recreated in a controlled experiment in a laboratory. Instead, scientists have to collect as many pieces of evidence as possible and see how well their theory explains their measurements. In history one cannot measure events in the past as one cannot go back in time! Therefore historians have to collect evidence from written records and other sources and use these to reach judgements about the causes of events. The idea that we can ‘prove’ what someone thought in the past is very controversial and many would say it is impossible. In literature, the emphasis tends to be on what an author meant when they wrote something. Critical Thinking Handout 2 So in these cases, the word ‘proof’ means something different, and if you got these mixed up you would be in trouble! You can not, for example, try to ask and answer questions about the causes of the collapse of the Soviet Union by recreating it in a test tube. Similarly, it would not be acceptable to say ‘Water contains hydrogen because someone said it did in the past’. Different disciplines require different kinds of proof, and these are not necessarily transferable between different domains. Let’s bring this back to critical thinking. In order to know what is an appropriate form of critical thinking, one needs to know what the best kind of thinking is for that situation. As teachers, you have to teach children how to identify the kinds of questions that might be asked and the appropriate ways in which those questions might be answered. This is at the heart of a more sophisticated understanding of ‘critical thinking’.