Probability

We express the probability that a given proposition is true (or that a given event has occurred or will occur) on a numerical scale between 0 and 1, expressed either as a decimal or as a fraction. For example the probability that a tossed coin will land heads-up is 0.5 or 1 2. Perhaps surprisingly, there are different ways in which to explain probability. We'll briefly consider three proportion, frequency, and rational expectation.1 First, proportion. Many arguments contain a premise that says...

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Of decriminalisation can use it in support of their cause their opponents can use it to back up their anti-decriminalisation stance (the latter might say, 'Only some members of parliament support. . .'). 3 Often people simply omit quantifiers. For instance, someone might protest Lecturers don't give students a chance to complain. At face value this might appear to convey the proposition that No lecturer (ever) gives a student a chance to complain. Yet it is likely that what the speaker really...

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Is clearly not an inductively forceful argument. If the only propositions you knew relevant to the conclusion were PI and P2, then you would be wrong to think that C is probably true. To say that all rodents have tails is the same as saying 'Every rodent has a tail', or 'Any rodent has a tail', or 'No rodent has no tail'. To say that most rodents have tails is to say that more than half of all rodents have tails, or that there are more rodents with tails than there are without them. But what...

Covering generalisations

In the politician case, the connecting premise was a generalisation (review the discussion of generalisations in Chapter 1 if you are not clear about what a generalisation is). Connecting premises are usually generalisations. But in the inflation case the connecting premise we used was a conditional (see Chapter 2). This is also common. However, there is an important relationship between conditionals and generalisations that must be appreciated. Consider the following propositions (a) If Betty...

Scorpios tend to be luckier than Libras

John does not believe in astrology, and therefore does not believe that one's fortune depends on the part of the year during which one is born. So he thinks this proposition is false. But John, wishing to avoid a painful disagreement, expresses himself by saying, 'Well, that may be true for you, but it isn't true for me'. As we have just seen, where implicit speaker-relativity is involved, the use of such phrases as 'true for you' is perfectly legitimate. But in the astrology case, the use of...

Abortion is immoral

According to the relativist view, when anti-abortionists say abortion is morally unacceptable and their opponents contradict them and say that it is morally acceptable, there is no real disagreement rather the two sides do not share the same moral preferences. Thus, for the relativist, value-statements are always speaker-relative, whether implicitly or explicitly. An apparent disagreement over a value is in this respect like that between Julie and John concerning chocolate versus vanilla ice...

Argument commentary

We have now completed our survey of our basic concepts and procedures of argument analysis. By 'argument analysis' we mean a two-stage process comprising first the reconstruction, then the assessment of the argument. At this point, we need to say a bit more about the final product of this process. When the analysis of an argument is undertaken, you may sometimes want to produce a piece of written work which summarises the analysis you have made. This should consist of three parts 1 The argument...

The scope of a generalisation

Consider the following hard generalisations 2 All black cows are herbivores. The subjects of these generalisations - what the generalisations are about - are cows and black cows, respectively. Both generalisations are true, and they stand in a special relationship. There are two aspects of this relationship. First, they attribute the same feature to their subjects (that of being herbivores). Second, the subject of the second is a subset of the first (all black cows are cows). Thus we say that...

Chocolate ice cream tastes better than vanilla

The implicit speaker-relativity of a sentence like this might be described by saying that the sentence is true for Julie, and not true for John. Upon hearing Julie assert this sentence, John might say, 'Well, that may be true for you, but it isn't true for me'. John might, in this case, simply be making the point about implicit speaker-relativity. If so, then that is all right he is quite right to do so. However, phrases such as 'true for me' are sometimes used in what appear to be factual...

2Vanilla ice cream tastes better than chocolate to John

These are two different propositions. There is certainly no logical conflict between them they could both be true. But in that case, Julie and John 2 There is one slight complication, however statements of this kind may mean that something is preferred or liked by most people. For example, this is plausibly what someone means who says 'Soured milk does not taste good'. Nevertheless, these statements are still implicitly relative, because they still depend for their truth on reference to...

More on generalisations

As we noted in Chapter 1, only hard generalisations can rightly be conveyed by using a quantifier-word like 'all', 'no', or 'every'. Indeed, that is the usual function of those words - to make it perfectly explicit that a hard generalisation is what is intended. For example someone at a meeting of Parliament might say, 'Every single MP in this chamber takes bribes', rather than 'The MPs in this chamber take bribes'. Soft generalisations, indeed, are very often expressed without any quantifier...

C1

In this case the argument whose conclusion is CI is a sub-argument for an extended argument whose conclusion is C2. You would first assess the argument from PI and P2 to CI you would then assess the argument from CI and P3 to C2. Finally, you would use these results to assess the total argument from PI, P2 and P3 to C2. Assessment is to be distinguished from reconstruction, which is discussed in more detail in the next chapter. Broadly speaking, assessment may be said to fall into two...

Implicit and explicit

Not only do actual statements of arguments typically include a lot of material that is inessential to the argument, they often exclude some of what is essential to the argument some essential propositions are left implicit, when our task in reconstruction is to make the argument fully explicit. To say that a proposition is implicit in an argument is to say that it is part of the argument intended by the arguer - either as a premise or as the conclusion - but that it has not actually been stated...

Extraneous material

The first step in analysing and reconstructing an argument is to identify its conclusion, then its premises. But much of what people say or write, when advancing an argument, plays no argumentative role. Much is there for emphasis, or is rhetorical, or plays some other role than that of expressing the propositions that properly constitute the argument. When reconstructing arguments, then, we have to hive off this extraneous material. Here's an example we've given each sentence a number in order...

Whenever The Cherry Trees Blossom The Weather Begins To Get Warmer

Democracy is the best system of government. Most people in the world believe in the superiority of democratic systems. Fallacy of majority belief P1 Most people believe in democratic systems. P2 Any belief held by the majority is true. C Democracy is the best system of government. a Our lecturers are always extolling the virtues of critical thinking, but they would say that wouldn't they They only keep their jobs if they've got students to teach. b It's not illegal for me to exaggerate my...

Iiiit is not an inductively forceful argument that is defeated for that person

It can even happen that an argument is rationally persuasive for you at one time, but not at a later time, because you have acquired new evidence which defeats the argument by suggesting that the conclusion is false, more strongly than the argument suggests its truth . To be strictly accurate, then, we should speak of rational persuasiveness for a person at a particular time. For the sake of simplicity, however, we have omitted this complication from what is already a rather complex definition....

Counterexample i A counterexample to a generalisation is a

Particular statement - a statement that is not a generalisation - that is the negation of an instance of the generalisation. For example 'Darcy Bussell is a great ballerina who is tall' is a counter-example to 'No great ballerinas are tall', ii A counter-example to an argument is an argument of the same form or pattern as the first argument that is clearly invalid or inductively non-forceful. It is used as an illustration to make it clear that the first argument is invalid or inductively...

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And so on, they invite pop stars to their parties and comport themselves as if they too were pop stars, just out to sell themselves really. In this example the speaker gets side-tracked into commenting upon the prime minister's suits and party guest-lists, and fails, beyond the vague charge that the government's policies are 'poll-driven nonsense', to offer a substantive criticism. Most of what is said is at best only obliquely relevant to the issue. 4 As with conclusions, there are certain...

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The focus of this book is written and spoken ways of persuading us to do things and to believe things. Every day we are bombarded with messages apparently telling us what to do or not to do, what to believe or not to believe buy this soft drink eat that breakfast cereal vote for Mrs Bloggs practise safe sex don't drink and drive don't use drugs boycott goods from a particular country abortion is murder meat is murder aliens have visited the earth the economy is sound capitalism is just...