RI Critical Thinking Notes 2023

RI KI Y5 Term 1 Critical Thinking I 1 Critical Thinking I AN OVERVIEW Words in bold indicate the main concepts with which you need to be familiar. This chart may be an over-simplification, but it serves as a useful summary or a flowchart for evaluating passages. Start: read passage Yes No. Eg. she is just giving an account of something Stop, no argument to evaluate Yes No No Yes Low probability High probability Stop, reject Stop, reject Yes No No Yes Stop, reject Stop, reject Yes No No Yes Stop, reject Stop, accept Stop, reject Stop, accept Note: FALLACIES are typical flaws in the argument that would result in it being rejected. BWT-Jan2006 Argument is UNRELIABLE Argument is RELIABLE Argument is NOT COGENT Argument is COGENT Does author intend to prove to you her conclusion? Passage is an ARGUMENT Passage is an EXPLANATION Does argument go from general to specific? Does conclusion follow with 100% probability? Argument is DEDUCTIVE Argument is INDUCTIVE Is conclusion likely to be true if premises are true? Is probability low or high? Argument is WEAK Argument is STRONG Is it possible for ALL the premises to be true AND the conclusion false? Argument is VALID Argument is INVALID Are the premises actually true? Argument is SOUND Argument is UNSOUND Are premises actually true? Does argument contain all known relevant information? Not a good deductive argument This is a good deductive argument Is argument circular? T1 T2 T3 T4 T5 T6 T7 T8

RI KI Y5 Term 1 Critical Thinking I 2 UNIT A: PARTS OF AN ARGUMENT In this unit, you will learn:  What an argument is  The basic components of an argument  How to identify an argument  How to distinguish between an argument and an explanation  How to distinguish between premises and conclusions in arguments  How to pick out implicit premises A1 What is an argument? When we think of an argument, some of us may visualize a couple of people locked in a debate or an angry dispute, but from the point of view of a logician an argument may not necessarily involve a dispute or even disagreement. In his point of view, an argument is a set of statements (or propositions, see * below) of which one – the one being argued for – is taken to be established as true on the basis of all the others. When we want to persuade others to accept the truth of a statement, one way of doing this is to offer them reasons or evidence in support of this statement. This is the essence of an argument. For example, someone might say: He must be older than he says he is. He told us he was thirty, but he has a daughter who is at least twenty-five years old. Here, reasons are offered for the conclusion that ‘he must be older than he says he is’. Look at the following simple examples of an argument. As you read them, think about which statement the author is trying to get you to accept (ie. the conclusion), and which statements are being offered as reasons for accepting the conclusion (ie. the premises): The bus is late. It must have broken down. Children learn languages much more quickly and speak them more fluently if they start to learn them from an early age. So if you want your children to be bilingual, you should speak two languages to them from the time they are born. She stood him up for their date. She obviously isn’t interested in being his girlfriend. If she’d wanted a serious relationship with him she wouldn’t have missed their date.

RI KI Y5 Term 1 Critical Thinking I 3 * Propositions: A proposition is a sentence that is true or false. The following are positive examples: - Wei Lin is in RI this year - today is Tuesday - software piracy is unethical and illeg al - every even number is the sum of two primes - all moral values are relative The following are negative examples; they are NOT propositions: - do not walk on the grass - is today Friday? - Oh, leave me alone - If you want more information, get in touch with me Why aren’t these considered propositions? A2 How to Identify Arguments Argument indicators Certain words are commonly used to indicate that someone is presenting a conclusion, for example ‘therefore’ and ‘so’. He told us he was thirty, but he has a dau ghter who is at least twenty-five years old. So, he must be older than he says he is. ‘Hence’ and ‘thus’ can also function in the same way as ‘so’. Other words also signal the presence of a conclusion, for instance, ‘must’ and ‘cannot’. In the example above, the word ‘must’ is used to show that the reasons offered force us to draw the conclusion. You can also use the word ‘cannot’ in a similar way: ‘He cannot be as young as he says he is.’ More indicator words: - ‘it follows that’ - ‘it can be concluded that’ - ‘proves’ - ‘implies’ - ‘establishes’ - ‘shows’ - ‘since’ - ‘because’ - ‘for’ - ‘follows from the fact that’ - ‘is established / implied by’ These indicator words do not guarantee that an argument is being offered as they have other uses. But you can use them as a genera l guide to assessing whether or not the passage contains an argument.

RI KI Y5 Term 1 Critical Thinking I 4 Passages which do not contain indicator words If there are no conclusion indicator words, look at each sentence in turn and ask: “Does the rest of the passage give me any extra information which tells me why I should believe this?” If the answer is ‘no’, then this sentence is not a conclusion. If the answer is ‘yes’, then the sentence is a conclusion. If none of the sentences in a passage is a conclusion, then the passage is not an argument: no conclusion, no argument. If one of the sentences in the passage is a conclusion supported by a reason or reasons in the passage, then the passage is an argument. Arguments vs Explanations Arguments are to be distinguished from explanations. A general rule is that arguments attempt to demonstrate that something is true whereas in explanations, the conclusion is assumed to be true already and the author is trying to explain how it happened. [TESTS] to distinguish arguments from explanations : not all of these are necessary each time you test for an argument; but go down the list when you are stumped by a passage that doesn’t seem that clear cut. a) The passage usually can fit the form of “R; therefore C.” b) X is an argument if the author intends to prove to you that C is true. (The presence of obligatory words – ‘should’, ‘ought’ – in C is a good indicator of such an intention.) c) X is an explanation, not an argument, if the author assumes the truth of C. d) When you have found a conclusion in a passage, rewrite the passage with the conclusion at the end, introduced by ‘So’. Read through this re -written passage to check that it makes sense. If it does, then you can be certain that this passage is an argument. There is no need to worry about whether the premises are true, or if they conclusively support the argument. Note: most of the time, for the short passages found in P2 Section B, due to space constraints, what is typically (as opposed to always) present are arguments rather than explanations. This guideline obviously does not apply for Section A long passages. Explanation or Argument? 1. We should restrict the production of ‘greenhouse’ gases because they are damaging the ozone layer. Argument 2. Napoleon died because he was poisoned with arsenic. Explanation 3. The dinosaurs died out because a huge meteor crashed into the Earth. Ex