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Logical assessment Logical assessment is the stage of argument assessment at which it is determined whether the argument is valid or invalid, and at which the degree of inductive force of invalid arguments is determined. Except where inductive inferences are concerned, it is sharply to be distinguished from factual assessment.

Practical reasoning Practical reasoning is the use of arguments whose conclusions recommend an action. See expected value.

Premise A premise in an argument is advanced as a reason for inferring the argument's conclusion.

Premise indicators These are expressions such as 'since, 'because', and 'for the reason that' that are often used to indicate a premise in an argument. As in the case of conclusion indicators, however, such words sometimes serve other purposes, such as indicating a causal relationship.

Principle of Charity According to this principle, if our aim is to discover the truth about a given issue, then we should reconstruct arguments so as to yield the maximum degree of rational persuasiveness for the relevant audience (which normally will include ourselves).

Probability The probability of a proposition is the degree to which it is likely to be true, where this degree is expressed as a fraction or decimal between 0 and 1. There are different ways of explaining this, such as proportion and frequency; but in this book the degree to which a proposition is likely to be true is taken to be the degree to which it would be perfectly rational to expect it to be true. Since this obviously depends on the evidence one has, the key concept is that of conditional probability: the degree to which it is rational to expect a proposition to be true given such-and-such evidence.

Proposition A proposition is the factual content expressed by a declarative sentence on a particular occasion of using (writing or uttering) the sentence. In particular, it is what is expressed that admits of being true or false. Different sentences can express the same proposition. For example 'Antony kissed Cleopatra' expresses the same proposition as 'Cleopatra was kissed by Antony'. Different propositions may be expressed by means of the same sentence. For example if Antony and Cleopatra each utter the sentence 'I'm hungry', they express different propositions, since they talk about different people. A sentence's prepositional content is independent of its rhetorical or emotive content.

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