2.13: Review of Major Points

We briefly explored the differences among descriptions, arguments, and explanations. Descriptions state the facts, report on states of mind, express values, and so forth. Arguments aim at convincing you that something is so or that something should be done. Explanations don't. They assume you are already convinced and instead try to show the cause, the motivation, or the sequence of events that led up to it. We noted that some arguments are strong enough to be called proofs.

Arguments are normally given to settle an issue one way or the other. An argument’s topic is more general than the issue it addresses.

Premise and conclusion indicator phrases serve as guideposts for detecting arguments. Almost all arguments have some implicit elements. The most common implicit premises are statements of common knowledge, definitions of words, principles of grammar, and rules of mathematics. Rewriting arguments in standard form is a helpful way to display their essential content. Arguments can have quite complex structure; for example, there are often sub-arguments within longer arguments.

Arguments can be evaluated as being deductively valid or inductively strong. With inductively strong arguments, the premises support the conclusion with high probability, but there is a small probability that the conclusion is false even if the premises are true, unlike with deductively valid arguments. If an argument has a counterexample, then it can’t be valid. All the topics of the present chapter get more detailed treatment later in the book. We humans seem to be better at detecting errors in other people’s reasoning than in our own, so it takes careful self-monitoring in order to reason logically about our own beliefs.